diff --git a/poincare/Makefile b/poincare/Makefile
index 788518f79..de32ca59a 100644
--- a/poincare/Makefile
+++ b/poincare/Makefile
@@ -4,23 +4,28 @@ objs += $(addprefix poincare/src/,\
   binary_operation.o\
   commutative_operation.o\
   context.o\
+  cosinus.o\
   expression.o\
   expression_lexer.o\
   expression_parser.o\
   float.o\
   fraction.o\
+  function.o\
   integer.o\
   leaf_expression.o\
   power.o\
   product.o\
+  sinus.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/,\
diff --git a/poincare/include/poincare.h b/poincare/include/poincare.h
index eeaf014ef..4b89926c0 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/cosinus.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/sinus.h>
 #include <poincare/subtraction.h>
 #include <poincare/symbol.h>
+#include <poincare/tangent.h>
 
 #endif
diff --git a/poincare/include/poincare/cosinus.h b/poincare/include/poincare/cosinus.h
new file mode 100644
index 000000000..5d4fc4e7a
--- /dev/null
+++ b/poincare/include/poincare/cosinus.h
@@ -0,0 +1,13 @@
+#ifndef POINCARE_COSINUS_H
+#define POINCARE_COSINUS_H
+
+#include <poincare/function.h>
+
+class Cosinus : public Function {
+  public:
+    Cosinus(Expression * arg): Function(arg, (char*) "cos") {}
+    float approximate(Context& context) override;
+    Type type() override;
+};
+
+#endif
diff --git a/poincare/include/poincare/expression.h b/poincare/include/poincare/expression.h
index 664ce6a64..af5e199f5 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,
+      Cosinus,
       Float,
       Fraction,
       Integer,
       Power,
       Product,
+      Sinus,
       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..2a8fa67fe
--- /dev/null
+++ b/poincare/include/poincare/function.h
@@ -0,0 +1,17 @@
+#ifndef POINCARE_FUNCTION_H
+#define POINCARE_FUNCTION_H
+
+#include <poincare/expression.h>
+
+class Function : public Expression {
+  public:
+    Function(Expression * arg, char* function_name): m_arg(arg), m_function_name(function_name) {}
+    ~Function();
+    ExpressionLayout * createLayout(ExpressionLayout * parent) override;
+  protected:
+    Expression * m_arg;
+  private:
+    char* m_function_name;
+};
+
+#endif
diff --git a/poincare/include/poincare/sinus.h b/poincare/include/poincare/sinus.h
new file mode 100644
index 000000000..5378dd789
--- /dev/null
+++ b/poincare/include/poincare/sinus.h
@@ -0,0 +1,13 @@
+#ifndef POINCARE_SINUS_H
+#define POINCARE_SINUS_H
+
+#include <poincare/function.h>
+
+class Sinus : public Function {
+  public:
+    Sinus(Expression * arg): Function(arg, (char*) "sin") {}
+    float approximate(Context& context) override;
+    Type type() override;
+};
+
+#endif
diff --git a/poincare/include/poincare/tangent.h b/poincare/include/poincare/tangent.h
new file mode 100644
index 000000000..f77593878
--- /dev/null
+++ b/poincare/include/poincare/tangent.h
@@ -0,0 +1,13 @@
+#ifndef POINCARE_TANGENT_H
+#define POINCARE_TANGENT_H
+
+#include <poincare/function.h>
+
+class Tangent : public Function {
+  public:
+    Tangent(Expression * arg): Function(arg, (char*) "tan") {}
+    float approximate(Context& context) override;
+    Type type() override;
+};
+
+#endif
diff --git a/poincare/src/cosinus.cpp b/poincare/src/cosinus.cpp
new file mode 100644
index 000000000..c21d00aa1
--- /dev/null
+++ b/poincare/src/cosinus.cpp
@@ -0,0 +1,11 @@
+#include <poincare/cosinus.h>
+#include "layout/horizontal_layout.h"
+
+Expression::Type Cosinus::type() {
+  return Expression::Type::Cosinus;
+}
+
+float Cosinus::approximate(Context& context) {
+  // FIXME: use cosinus obviously.
+  return m_arg->approximate(context);
+}
diff --git a/poincare/src/expression_lexer.l b/poincare/src/expression_lexer.l
index 5dd2bb7b4..008e5fca5 100644
--- a/poincare/src/expression_lexer.l
+++ b/poincare/src/expression_lexer.l
@@ -43,6 +43,9 @@ class Expression;
 
 [0-9]+ { yylval->string = yytext; return(INTEGER); }
 [A-Za-z]+ { yylval->string = yytext; return(SYMBOL); }
+sin {return(SINUS);}
+cos {return(COSINUS);}
+tan {return(TANGENT);}
 \+ { return(PLUS); }
 \- { return(MINUS); }
 \* { return(MULTIPLY); }
diff --git a/poincare/src/expression_parser.y b/poincare/src/expression_parser.y
index 505f1505b..bb3dd2b14 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 SINUS
+%token COSINUS
+%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     { $$ = $2; }
+  | SINUS LEFT_PARENTHESIS exp RIGHT_PARENTHESIS     { $$ = new Sinus($3); }
+  | COSINUS LEFT_PARENTHESIS exp RIGHT_PARENTHESIS     { $$ = new Cosinus($3); }
+  | TANGENT LEFT_PARENTHESIS exp RIGHT_PARENTHESIS     { $$ = new Tangent($3); }
 ;
 
 %%
diff --git a/poincare/src/function.cpp b/poincare/src/function.cpp
new file mode 100644
index 000000000..e7e230d11
--- /dev/null
+++ b/poincare/src/function.cpp
@@ -0,0 +1,10 @@
+#include <poincare/function.h>
+#include "layout/function_layout.h"
+
+Function::~Function() {
+  delete m_arg;
+}
+
+ExpressionLayout * Function::createLayout(ExpressionLayout * parent) {
+  return new FunctionLayout(parent, m_function_name, m_arg);
+}
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..cc64c78af 100644
--- a/poincare/src/layout/horizontal_layout.cpp
+++ b/poincare/src/layout/horizontal_layout.cpp
@@ -6,7 +6,7 @@ extern "C" {
 #include "string_layout.h"
 
 HorizontalLayout::HorizontalLayout(ExpressionLayout * parent, Expression * left_expression, char symbol, Expression * right_expression) :
-ExpressionLayout(parent ) {
+ExpressionLayout(parent) {
   m_children[0] = left_expression->createLayout(this);
 
   char string[2] = {symbol, '\0'};
diff --git a/poincare/src/sinus.cpp b/poincare/src/sinus.cpp
new file mode 100644
index 000000000..6e831cb2e
--- /dev/null
+++ b/poincare/src/sinus.cpp
@@ -0,0 +1,11 @@
+#include <poincare/sinus.h>
+#include "layout/horizontal_layout.h"
+
+Expression::Type Sinus::type() {
+  return Expression::Type::Sinus;
+}
+
+float Sinus::approximate(Context& context) {
+  // FIXME: use sinus obviously.
+  return m_arg->approximate(context);
+}
diff --git a/poincare/src/tangent.cpp b/poincare/src/tangent.cpp
new file mode 100644
index 000000000..71e9d3191
--- /dev/null
+++ b/poincare/src/tangent.cpp
@@ -0,0 +1,11 @@
+#include <poincare/tangent.h>
+#include "layout/horizontal_layout.h"
+
+Expression::Type Tangent::type() {
+  return Expression::Type::Tangent;
+}
+
+float Tangent::approximate(Context& context) {
+  // FIXME: use tangent obviously.
+  return m_arg->approximate(context);
+}