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# Repérer un angle droit dans une figure

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## Introduction

Beaucoup de figures géométriques ont des coins. On peut dire qu'un coin est un angle droit si on peut faire rentrer parfaitement un petit carré à l’intérieur.

### L'exemple de ce trapèze :

A trapezoid. The direction of each side is as follows, beginning at the top and continuing in a clockwise pattern: straight line to the right, straight line down and left, straight line to the left, straight line up.
On dessine un carré dans chaque coin.
A trapezoid with a square in each corner. The direction of each side is as follows, beginning at the top and continuing in a clockwise pattern: straight line to the right, straight line down and left, straight line to the left, straight line up.
Dans quels coins le petit carré est-il rentré parfaitement ?
A trapezoid with a square in each corner. There are 2 green squares in the upper and lower left corners. There are 2 red squares in the upper and lower right corners. Each green square is labeled right angle and each red square is labeled not a right angle. The direction of each side is as follows, beginning at the top and continuing in a clockwise pattern: straight line to the right, straight line down and left, straight line to the left, straight line up.
Ce trapèze a deux angles droits.

## À vous !

D'abord, voici trois figures où on a mis en évidence un ou des angles droits.
A rectangle with a square in each corner. The direction of each side is as follows, beginning at the top and continuing in a clockwise pattern: straight line to the right, straight line down, straight line to the left, straight line up.
A quadrilateral with a square in one corner. The direction of each side is as follows, beginning at the top and continuing in a clockwise pattern: straight line down and right, straight line down and left, straight line up and left, straight line up and right.
A right triangle with a square in one corner. The direction of each side is as follows, beginning at the top and continuing in a clockwise pattern: straight line to the right, straight line down and left, straight line up.
A vous.
Combien y a-t-il d'angles droits dans un carré ?
A square shape with 4 sides. The direction of each side is as follows, beginning at the top and continuing in a clockwise pattern: straight line to the right, straight line down, straight line to the left, straight line up.

Combien y a-t-il d'angles droits dans ce pentagone ?
A pentagon shape with 5 sides. The direction of each side is as follows, beginning at the top and continuing in a clockwise pattern: straight line to the right, straight line down and right, straight line down and left, straight line to the left, straight line up.

## Un dernier exercice

Combien y a-t-il d'angles droits dans cette figure ?
A shape with 9 sides. The direction of each side is as follows, beginning at the top and continuing in a clockwise pattern: straight line to the right, straight line down and right, straight line to the right, straight line down and left, straight line down and right, straight line down and left, straight line to the left, straight line up, straight line up and right.

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