# Formulaire:mathématiques - Géométrie - Cerne

## Cerne

A circle is a basic shape consisting of the points at a given distance from a given point on a plane.

### Définitions:

• r: Rayon
• d: Diamètre
• U: Périmètre
• A: Aire

#### Circonférence

The circumference U is the distance around a closed curve.

$${\color{blue} {U}} = 2 \times \pi \times {\color{red} {r} }$$
U = Périmètre
r = Rayon

$${\color{red} {r}} = \frac{ {\color{blue} {U} } }{ 2 \times \pi }$$
r = Rayon
U = Périmètre

$${\color{blue} {U}} = \pi \times {\color{red} {d} }$$
U = Périmètre
d = Diamètre

$${\color{red} {d}} = \frac{ {\color{blue} {U} } }{ \pi }$$
d = Diamètre
U = Périmètre

#### Cercle zone

The region inside a circle.

$${\color{OliveGreen} {A}} = \pi \times {\color{red} {r} }^{2}$$
A = Aire
r = Rayon

$${\color{red} {r}} = \sqrt{ \frac{\color{OliveGreen} {A}}{\pi} }$$
r = Rayon
A = Aire

$${\color{OliveGreen} {A}} = \frac{\pi}{4} \times {\color{red} {d} }^{2}$$
A = Aire
d = Diamètre

$${\color{red} {d}} = \sqrt{ \frac{4 \times {\color{OliveGreen} {A} } }{\pi}}$$
d = Diamètre
A = Aire