# Equilateral triangle calculator (a)

Please enter one property of the equilateral triangle

Use symbols: a, h, T, p, r, R

You have entered side a.

### Equilateral triangle.

Sides: a = 6   b = 6   c = 6

Area: T = 15.58884572681
Perimeter: p = 18
Semiperimeter: s = 9

Angle ∠ A = α = 60° = 1.04771975512 rad
Angle ∠ B = β = 60° = 1.04771975512 rad
Angle ∠ C = γ = 60° = 1.04771975512 rad

Height: ha = 5.19661524227
Height: hb = 5.19661524227
Height: hc = 5.19661524227

Median: ma = 5.19661524227
Median: mb = 5.19661524227
Median: mc = 5.19661524227

Vertex coordinates: A[6; 0] B[0; 0] C[3; 5.19661524227]
Centroid: CG[3; 1.73220508076]
Coordinates of the circumscribed circle: U[3; 1.73220508076]
Coordinates of the inscribed circle: I[3; 1.73220508076]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 120° = 1.04771975512 rad
∠ B' = β' = 120° = 1.04771975512 rad
∠ C' = γ' = 120° = 1.04771975512 rad

# How did we calculate this triangle?

### 1. Input data entered: side a ### 2. From side a we calculate b,c: Now we know the lengths of all three sides of the triangle and the triangle is uniquely determined. Next we calculate another its characteristics - same procedure as calculation of the triangle from the known three sides SSS. ### 3. The triangle circumference is the sum of the lengths of its three sides ### 4. Semiperimeter of the triangle ### 5. The triangle area using Heron's formula ### 6. Calculate the heights of the triangle from its area. ### 7. Calculation of the inner angles of the triangle using a Law of Cosines    