# 1. How to find the area of a circle with the radius

Know: radius

What is its area?

Formula for the area of a circle: A = π.R^{2}.

- Area of a circle: A
- π ≈ 3,14159
- Radius: R

## 2. How to find the area of a circle with the diameter

Know: Diameter

What is its area?

Formula for the area of a circle: $A = \frac{1}{4}.\pi .{D^2}$

- Area of a circle: A
- π ≈ 3,14159
- Diameter: D

Note: D = AB = 2R => D/2 = R => A = π.(D/2)^{2}. = 0,25.π.D^{2}