diff --git a/app/Makefile b/app/Makefile
index fba1326d1..d662c1a4d 100644
--- a/app/Makefile
+++ b/app/Makefile
@@ -1,6 +1,6 @@
 app_objs += $(addprefix app/,\
 						app.o\
-						text_input.o)
+						utils.o)
 products += $(app_objs) app.elf app.hex app.bin
 
 app.elf: $(app_objs)
diff --git a/app/app.cpp b/app/app.cpp
index 043984995..eede4f5e7 100644
--- a/app/app.cpp
+++ b/app/app.cpp
@@ -6,7 +6,7 @@ extern "C" {
 
 #include <poincare.h>
 
-#include "text_input.h"
+#include "utils.h"
 
 void draw_lines_from_center() {
   KDCoordinate width = SCREEN_WIDTH;
@@ -60,16 +60,6 @@ void funnyPlot() {
   delete e;
 }
 
-static void clear_screen() {
-  KDRect r;
-  r.x = 0;
-  r.y = 0;
-  r.width = SCREEN_WIDTH;
-  r.height = SCREEN_HEIGHT;
-  KDFillRect(r, 0x00);
-}
-
-
 static void interactive_expression_parsing() {
   while (1) {
     char * text_input = get_text();
diff --git a/app/text_input.cpp b/app/utils.cpp
similarity index 92%
rename from app/text_input.cpp
rename to app/utils.cpp
index 522203310..f0e1c16d4 100644
--- a/app/text_input.cpp
+++ b/app/utils.cpp
@@ -7,6 +7,15 @@ extern "C" {
 
 #define PROMPT_HEIGHT 30
 
+void clear_screen() {
+  KDRect r;
+  r.x = 0;
+  r.y = 0;
+  r.width = SCREEN_WIDTH;
+  r.height = SCREEN_HEIGHT;
+  KDFillRect(r, 0x00);
+}
+
 static void clear_prompt() {
   KDRect r;
   r.x = 0;
diff --git a/app/text_input.h b/app/utils.h
similarity index 61%
rename from app/text_input.h
rename to app/utils.h
index b7490c2ff..ca78fcae1 100644
--- a/app/text_input.h
+++ b/app/utils.h
@@ -1,8 +1,10 @@
-#ifndef APP_TEXTINPUT_H
-#define APP_TEXTINPUT_H
+#ifndef APP_UTILS_H
+#define APP_UTILS_H
 
 /* Returns a pointer to an input text, allocated by the functions (it is thus
  * the caller's role to free it). */
 char* get_text();
 
-#endif // APP_TEXTINPUT_H
+void clear_screen();
+
+#endif // APP_UTILS_H
diff --git a/poincare/Makefile b/poincare/Makefile
index a3d430325..2d7202235 100644
--- a/poincare/Makefile
+++ b/poincare/Makefile
@@ -4,23 +4,28 @@ objs += $(addprefix poincare/src/,\
   binary_operation.o\
   commutative_operation.o\
   context.o\
+  cosine.o\
   expression.o\
   expression_lexer.o\
   expression_parser.o\
   float.o\
   fraction.o\
+  function.o\
   integer.o\
   leaf_expression.o\
   power.o\
   product.o\
+  sine.o\
   subtraction.o\
   symbol.o\
+  tangent.o\
 )
 objs += $(addprefix poincare/src/layout/,\
+  exponent_layout.o\
   expression_layout.o\
   fraction_layout.o\
+  function_layout.o\
   horizontal_layout.o\
-  exponent_layout.o\
   string_layout.o\
 )
 objs += $(addprefix poincare/src/simplify/,\
@@ -35,6 +40,7 @@ tests += $(addprefix poincare/test/,\
   product.cpp\
   simplify.cpp\
   simplify_addition_integer.cpp\
+  trigo.cpp\
   subtraction.cpp\
 )
 
diff --git a/poincare/include/poincare.h b/poincare/include/poincare.h
index eeaf014ef..21b774e7c 100644
--- a/poincare/include/poincare.h
+++ b/poincare/include/poincare.h
@@ -3,13 +3,17 @@
 
 #include <poincare/addition.h>
 #include <poincare/context.h>
+#include <poincare/cosine.h>
 #include <poincare/expression.h>
-#include <poincare/fraction.h>
 #include <poincare/float.h>
+#include <poincare/fraction.h>
+#include <poincare/function.h>
 #include <poincare/integer.h>
 #include <poincare/power.h>
 #include <poincare/product.h>
+#include <poincare/sine.h>
 #include <poincare/subtraction.h>
 #include <poincare/symbol.h>
+#include <poincare/tangent.h>
 
 #endif
diff --git a/poincare/include/poincare/cosine.h b/poincare/include/poincare/cosine.h
new file mode 100644
index 000000000..31f376375
--- /dev/null
+++ b/poincare/include/poincare/cosine.h
@@ -0,0 +1,14 @@
+#ifndef POINCARE_COSINE_H
+#define POINCARE_COSINE_H
+
+#include <poincare/function.h>
+
+class Cosine : public Function {
+  public:
+    Cosine(Expression * arg, bool clone_arg=true): Function(arg, (char*) "cos", clone_arg) {}
+    float approximate(Context& context) override;
+    Type type() override;
+    Expression * clone() override;
+};
+
+#endif
diff --git a/poincare/include/poincare/expression.h b/poincare/include/poincare/expression.h
index 3fe1bbf8f..cedb2ec46 100644
--- a/poincare/include/poincare/expression.h
+++ b/poincare/include/poincare/expression.h
@@ -10,13 +10,16 @@ class Expression {
   public:
     enum class Type : uint8_t {
       Addition,
+      Cosine,
       Float,
       Fraction,
       Integer,
       Power,
       Product,
+      Sine,
       Subtraction,
-      Symbol
+      Symbol,
+      Tangent,
     };
     static Expression * parse(char const * string);
     virtual ~Expression();
diff --git a/poincare/include/poincare/function.h b/poincare/include/poincare/function.h
new file mode 100644
index 000000000..e02e7e388
--- /dev/null
+++ b/poincare/include/poincare/function.h
@@ -0,0 +1,19 @@
+#ifndef POINCARE_FUNCTION_H
+#define POINCARE_FUNCTION_H
+
+#include <poincare/expression.h>
+
+class Function : public Expression {
+  public:
+    Function(Expression * arg, char* function_name, bool clone_operands=true);
+    ~Function();
+    ExpressionLayout * createLayout(ExpressionLayout * parent) override;
+    Expression * operand(int i) override;
+    int numberOfOperands() override;
+  protected:
+    Expression * m_arg;
+  private:
+    char* m_function_name;
+};
+
+#endif
diff --git a/poincare/include/poincare/sine.h b/poincare/include/poincare/sine.h
new file mode 100644
index 000000000..fe53563a0
--- /dev/null
+++ b/poincare/include/poincare/sine.h
@@ -0,0 +1,14 @@
+#ifndef POINCARE_SINE_H
+#define POINCARE_SINE_H
+
+#include <poincare/function.h>
+
+class Sine : public Function {
+  public:
+    Sine(Expression * arg, bool clone_arg=true): Function(arg, (char*) "sin", clone_arg) {}
+    float approximate(Context& context) override;
+    Type type() override;
+    Expression * clone() override;
+};
+
+#endif
diff --git a/poincare/include/poincare/tangent.h b/poincare/include/poincare/tangent.h
new file mode 100644
index 000000000..06ffbae06
--- /dev/null
+++ b/poincare/include/poincare/tangent.h
@@ -0,0 +1,14 @@
+#ifndef POINCARE_TANGENT_H
+#define POINCARE_TANGENT_H
+
+#include <poincare/function.h>
+
+class Tangent : public Function {
+  public:
+    Tangent(Expression * arg, bool clone_arg=true): Function(arg, (char*) "tan", clone_arg) {}
+    float approximate(Context& context) override;
+    Type type() override;
+    Expression * clone() override;
+};
+
+#endif
diff --git a/poincare/src/addition.cpp b/poincare/src/addition.cpp
index cb4080b33..15795ee7b 100644
--- a/poincare/src/addition.cpp
+++ b/poincare/src/addition.cpp
@@ -14,6 +14,5 @@ float Addition::operateApproximatevelyOn(float a, float b) {
 }
 
 ExpressionLayout * Addition::createLayout(ExpressionLayout * parent) {
-  //FIXME: There can be more than two operands now! :-)
-  return new HorizontalLayout(parent, operand(0), '+', operand(1));
+  return new HorizontalLayout(parent, m_operands, m_numberOfOperands, '+');
 }
diff --git a/poincare/src/commutative_operation.cpp b/poincare/src/commutative_operation.cpp
index 929908076..37252e0a0 100644
--- a/poincare/src/commutative_operation.cpp
+++ b/poincare/src/commutative_operation.cpp
@@ -30,6 +30,7 @@ int CommutativeOperation::numberOfOperands() {
 }
 
 Expression * CommutativeOperation::operand(int i) {
+  assert(i < m_numberOfOperands);
   return m_operands[i];
 }
 
diff --git a/poincare/src/cosine.cpp b/poincare/src/cosine.cpp
new file mode 100644
index 000000000..8fafad923
--- /dev/null
+++ b/poincare/src/cosine.cpp
@@ -0,0 +1,15 @@
+#include <poincare/cosine.h>
+#include "layout/horizontal_layout.h"
+
+Expression * Cosine::clone() {
+  return new Cosine(m_arg, true);
+}
+
+Expression::Type Cosine::type() {
+  return Expression::Type::Cosine;
+}
+
+float Cosine::approximate(Context& context) {
+  // FIXME: use cosine obviously.
+  return m_arg->approximate(context);
+}
diff --git a/poincare/src/expression_lexer.l b/poincare/src/expression_lexer.l
index 5dd2bb7b4..26a2dffdc 100644
--- a/poincare/src/expression_lexer.l
+++ b/poincare/src/expression_lexer.l
@@ -42,6 +42,9 @@ class Expression;
 %%
 
 [0-9]+ { yylval->string = yytext; return(INTEGER); }
+sin {return(SINE);}
+cos {return(COSINE);}
+tan {return(TANGENT);}
 [A-Za-z]+ { yylval->string = yytext; return(SYMBOL); }
 \+ { return(PLUS); }
 \- { return(MINUS); }
diff --git a/poincare/src/expression_parser.y b/poincare/src/expression_parser.y
index 505f1505b..43c501e64 100644
--- a/poincare/src/expression_parser.y
+++ b/poincare/src/expression_parser.y
@@ -54,6 +54,9 @@ void poincare_expression_yyerror(void * scanner, Expression ** expressionOutput,
 %token MULTIPLY
 %token DIVIDE
 %token POW
+%token SINE
+%token COSINE
+%token TANGENT
 %token LEFT_PARENTHESIS
 %token RIGHT_PARENTHESIS
 
@@ -85,6 +88,9 @@ exp:
   | exp DIVIDE exp   { Expression * terms[2] = {$1,$3}; $$ = new Fraction(terms, false); }
   | exp POW exp      { Expression * terms[2] = {$1,$3}; $$ = new Power(terms, false); }
   | LEFT_PARENTHESIS exp RIGHT_PARENTHESIS     { $$ = $2; }
+  | SINE LEFT_PARENTHESIS exp RIGHT_PARENTHESIS     { $$ = new Sine($3); }
+  | COSINE LEFT_PARENTHESIS exp RIGHT_PARENTHESIS     { $$ = new Cosine($3); }
+  | TANGENT LEFT_PARENTHESIS exp RIGHT_PARENTHESIS     { $$ = new Tangent($3); }
 ;
 
 %%
diff --git a/poincare/src/function.cpp b/poincare/src/function.cpp
new file mode 100644
index 000000000..e0ac86286
--- /dev/null
+++ b/poincare/src/function.cpp
@@ -0,0 +1,35 @@
+extern "C" {
+#include <stdlib.h>
+}
+#include <poincare/function.h>
+#include "layout/function_layout.h"
+
+Function::Function(Expression * arg, char* function_name, bool clone_operands) {
+  m_arg = (Expression *)malloc(sizeof(Expression));
+  m_function_name = function_name;
+  if (clone_operands) {
+    m_arg = arg->clone();
+  } else {
+    m_arg = arg;
+  }
+}
+
+Function::~Function() {
+  delete m_arg;
+}
+
+ExpressionLayout * Function::createLayout(ExpressionLayout * parent) {
+  return new FunctionLayout(parent, m_function_name, m_arg);
+}
+
+Expression * Function::operand(int i) {
+  if (i==0) {
+    return m_arg;
+  } else {
+    return nullptr;
+  }
+}
+
+int Function::numberOfOperands() {
+  return 1;
+}
diff --git a/poincare/src/layout/function_layout.cpp b/poincare/src/layout/function_layout.cpp
new file mode 100644
index 000000000..02bc5410b
--- /dev/null
+++ b/poincare/src/layout/function_layout.cpp
@@ -0,0 +1,73 @@
+extern "C" {
+#include <kandinsky.h>
+#include <assert.h>
+}
+#include "function_layout.h"
+#include "string_layout.h"
+
+// This code seems like a duplicate of the horizontal layout but it isn't, indeed the horizontal
+// layout is used to print the same operation applied to different expressions such that:
+//   "expr_1 + epr_2 + expr_3 + expr_4".
+// Here we want the pattern
+//   FUNCTION_NAME(expr).
+// Thus the code in horizontal layer is not really reusable.
+
+FunctionLayout::FunctionLayout(ExpressionLayout * parent, char* function_name, Expression * argument) :
+ExpressionLayout(parent) {
+  m_children[0] = new StringLayout(this, function_name, 1);
+
+  char string[2] = {'(', '\0'};
+  m_children[1] = new StringLayout(this, string, 1);
+
+  m_children[2] = argument->createLayout(this);
+
+  string[0] = ')';
+  m_children[3] = new StringLayout(this, string, 1);
+}
+
+FunctionLayout::~FunctionLayout() {
+  for (int i(0); i<4; i++) {
+    delete m_children[i];
+  }
+}
+
+void FunctionLayout::render(KDPoint point) { }
+
+KDSize FunctionLayout::computeSize() {
+  KDSize size = (KDSize){.width = 0, .height = 0};
+  int i = 0;
+  while (ExpressionLayout * c = child(i++)) {
+    KDSize childSize = c->size();
+    size.width += childSize.width;
+    if (childSize.height > size.height) {
+      size.height = childSize.height;
+    }
+  }
+  return size;
+}
+
+ExpressionLayout * FunctionLayout::child(uint16_t index) {
+  if (index >= 4) {
+    return nullptr;
+  }
+  return m_children[index];
+}
+
+KDPoint FunctionLayout::positionOfChild(ExpressionLayout * child) {
+  KDPoint position = (KDPoint){.x = 0, .y = 0};
+  uint16_t index = 0;
+  for (int i=0;i<4;i++) {
+    if (m_children[i] == child) {
+      index = i;
+      break;
+    }
+  }
+  if (index > 0) {
+    ExpressionLayout * previousChild = m_children[index-1];
+    assert(previousChild != nullptr);
+    position.x = previousChild->origin().x + previousChild->size().width;
+  }
+  position.y = (size().height - child->size().height)/2;
+  return position;
+}
+
diff --git a/poincare/src/layout/function_layout.h b/poincare/src/layout/function_layout.h
new file mode 100644
index 000000000..0b689dfcf
--- /dev/null
+++ b/poincare/src/layout/function_layout.h
@@ -0,0 +1,21 @@
+#ifndef POINCARE_FUNCTION_LAYOUT_H
+#define POINCARE_FUNCTION_LAYOUT_H
+
+#include <poincare/expression.h>
+#include <poincare/expression_layout.h>
+
+class FunctionLayout : public ExpressionLayout {
+  public:
+    FunctionLayout(ExpressionLayout * parent, char* function_name, Expression * arg);
+    ~FunctionLayout();
+  protected:
+    void render(KDPoint point) override;
+    KDSize computeSize() override;
+    ExpressionLayout * child(uint16_t index) override;
+    KDPoint positionOfChild(ExpressionLayout * child) override;
+  private:
+    ExpressionLayout * m_children[4];
+};
+
+#endif
+
diff --git a/poincare/src/layout/horizontal_layout.cpp b/poincare/src/layout/horizontal_layout.cpp
index e1297a0d2..eebc343b0 100644
--- a/poincare/src/layout/horizontal_layout.cpp
+++ b/poincare/src/layout/horizontal_layout.cpp
@@ -1,29 +1,31 @@
 extern "C" {
-#include <kandinsky.h>
 #include <assert.h>
+#include <kandinsky.h>
+#include <stdlib.h>
 }
 #include "horizontal_layout.h"
 #include "string_layout.h"
 
-HorizontalLayout::HorizontalLayout(ExpressionLayout * parent, Expression * left_expression, char symbol, Expression * right_expression) :
-ExpressionLayout(parent ) {
-  m_children[0] = left_expression->createLayout(this);
-
+HorizontalLayout::HorizontalLayout(ExpressionLayout * parent, Expression ** operands,int number_of_operands, char symbol) : ExpressionLayout(parent) {
+  assert(number_of_operands > 0);
+  m_number_of_children = 2*number_of_operands-1;
+  m_children_layouts = (ExpressionLayout **)malloc(m_number_of_children*sizeof(ExpressionLayout *));
   char string[2] = {symbol, '\0'};
-  m_children[1] = new StringLayout(this, string, 1);
-
-  m_children[2] = right_expression->createLayout(this);
+  m_children_layouts[0] = operands[0]->createLayout(this);
+  for (int i=1; i<number_of_operands; i++) {
+    m_children_layouts[2*i-1] = new StringLayout(this, string, 1);
+    m_children_layouts[2*i] = operands[i]->createLayout(this);
+  }
 }
 
 HorizontalLayout::~HorizontalLayout() {
-  delete m_children[2];
-  delete m_children[1];
-  delete m_children[0];
+  for (int i=0; i<m_number_of_children; i++) {
+    delete m_children_layouts[i];
+  }
+  free(m_children_layouts);
 }
 
-void HorizontalLayout::render(KDPoint point) {
-  // Nothing to render "per se"
-}
+void HorizontalLayout::render(KDPoint point) { }
 
 KDSize HorizontalLayout::computeSize() {
   KDSize size = (KDSize){.width = 0, .height = 0};
@@ -39,23 +41,25 @@ KDSize HorizontalLayout::computeSize() {
 }
 
 ExpressionLayout * HorizontalLayout::child(uint16_t index) {
-  if (index >= 3) {
+  assert(index <= m_number_of_children);
+  if (index < m_number_of_children) {
+    return m_children_layouts[index];
+  } else {
     return nullptr;
   }
-  return m_children[index];
 }
 
 KDPoint HorizontalLayout::positionOfChild(ExpressionLayout * child) {
   KDPoint position = (KDPoint){.x = 0, .y = 0};
   uint16_t index = 0;
-  for (int i=0;i<3;i++) {
-    if (m_children[i] == child) {
+  for (int i=0;i<m_number_of_children;i++) {
+    if (m_children_layouts[i] == child) {
       index = i;
       break;
     }
   }
   if (index > 0) {
-    ExpressionLayout * previousChild = m_children[index-1];
+    ExpressionLayout * previousChild = m_children_layouts[index-1];
     assert(previousChild != nullptr);
     position.x = previousChild->origin().x + previousChild->size().width;
   }
diff --git a/poincare/src/layout/horizontal_layout.h b/poincare/src/layout/horizontal_layout.h
index d4cb6a04a..0ee133f5c 100644
--- a/poincare/src/layout/horizontal_layout.h
+++ b/poincare/src/layout/horizontal_layout.h
@@ -6,7 +6,7 @@
 
 class HorizontalLayout : public ExpressionLayout {
   public:
-    HorizontalLayout(ExpressionLayout * parent, Expression * left_expression, char symbol, Expression * right_expression);
+    HorizontalLayout(ExpressionLayout * parent, Expression ** operands, int number_of_children, char symbol);
     ~HorizontalLayout();
   protected:
     void render(KDPoint point) override;
@@ -14,7 +14,8 @@ class HorizontalLayout : public ExpressionLayout {
     ExpressionLayout * child(uint16_t index) override;
     KDPoint positionOfChild(ExpressionLayout * child) override;
   private:
-    ExpressionLayout * m_children[3];
+    int m_number_of_children;
+    ExpressionLayout ** m_children_layouts;
 };
 
 #endif
diff --git a/poincare/src/product.cpp b/poincare/src/product.cpp
index fc888bfd8..36c93dcba 100644
--- a/poincare/src/product.cpp
+++ b/poincare/src/product.cpp
@@ -17,6 +17,5 @@ Expression::Type Product::type() {
 }
 
 ExpressionLayout * Product::createLayout(ExpressionLayout * parent) {
-  //FIXME: There can be more than two factors now! :-)
-  return new HorizontalLayout(parent, operand(0), '*', operand(1));
+  return new HorizontalLayout(parent, m_operands, m_numberOfOperands, '*');
 }
diff --git a/poincare/src/sine.cpp b/poincare/src/sine.cpp
new file mode 100644
index 000000000..fb3d7003c
--- /dev/null
+++ b/poincare/src/sine.cpp
@@ -0,0 +1,15 @@
+#include <poincare/sine.h>
+#include "layout/horizontal_layout.h"
+
+Expression * Sine::clone() {
+  return new Sine(m_arg, true);
+}
+
+Expression::Type Sine::type() {
+  return Expression::Type::Sine;
+}
+
+float Sine::approximate(Context& context) {
+  // FIXME: use sine obviously.
+  return m_arg->approximate(context);
+}
diff --git a/poincare/src/subtraction.cpp b/poincare/src/subtraction.cpp
index 7f82f02db..448553f2a 100644
--- a/poincare/src/subtraction.cpp
+++ b/poincare/src/subtraction.cpp
@@ -14,5 +14,5 @@ Expression::Type Subtraction::type() {
 }
 
 ExpressionLayout * Subtraction::createLayout(ExpressionLayout * parent) {
-  return new HorizontalLayout(parent, m_operands[0], '-', m_operands[1]);
+  return new HorizontalLayout(parent, m_operands, 2, '-');
 }
diff --git a/poincare/src/tangent.cpp b/poincare/src/tangent.cpp
new file mode 100644
index 000000000..6eb92af4c
--- /dev/null
+++ b/poincare/src/tangent.cpp
@@ -0,0 +1,15 @@
+#include <poincare/tangent.h>
+#include "layout/horizontal_layout.h"
+
+Expression * Tangent::clone() {
+  return new Tangent(m_arg, true);
+}
+
+Expression::Type Tangent::type() {
+  return Expression::Type::Tangent;
+}
+
+float Tangent::approximate(Context& context) {
+  // FIXME: use tangent obviously.
+  return m_arg->approximate(context);
+}
diff --git a/poincare/test/trigo.cpp b/poincare/test/trigo.cpp
new file mode 100644
index 000000000..700ac5b64
--- /dev/null
+++ b/poincare/test/trigo.cpp
@@ -0,0 +1,21 @@
+#include <quiz.h>
+#include <poincare.h>
+#include <assert.h>
+
+QUIZ_CASE(poincare_parse_trigo) {
+  {
+    Expression * e = Expression::parse("sin(0)");
+    Expression * e2 = e->simplify();
+    assert(e2->type() == Expression::Type::Sine);
+  }
+  {
+    Expression * e = Expression::parse("cos(0)");
+    Expression * e2 = e->simplify();
+    assert(e2->type() == Expression::Type::Cosine);
+  }
+  {
+    Expression * e = Expression::parse("tan(0)");
+    Expression * e2 = e->simplify();
+    assert(e2->type() == Expression::Type::Tangent);
+  }
+}
diff --git a/quiz/src/runner.c b/quiz/src/runner.c
index a19e202d8..bb76367cb 100644
--- a/quiz/src/runner.c
+++ b/quiz/src/runner.c
@@ -10,7 +10,6 @@ void print(char * message) {
   line_y += line_height;
   if (line_y > SCREEN_HEIGHT) {
     line_y = 0;
-    ion_getchar();
     // Clear screen maybe?
   }
 }