# 25 25 30 triangle

### Acute isosceles triangle.

Sides: a = 25   b = 25   c = 30

Area: T = 300
Perimeter: p = 80
Semiperimeter: s = 40

Angle ∠ A = α = 53.13301023542° = 53°7'48″ = 0.9277295218 rad
Angle ∠ B = β = 53.13301023542° = 53°7'48″ = 0.9277295218 rad
Angle ∠ C = γ = 73.74397952917° = 73°44'23″ = 1.28770022176 rad

Height: ha = 24
Height: hb = 24
Height: hc = 20

Median: ma = 24.62221445045
Median: mb = 24.62221445045
Median: mc = 20

Inradius: r = 7.5
Circumradius: R = 15.625

Vertex coordinates: A[30; 0] B[0; 0] C[15; 20]
Centroid: CG[15; 6.66766666667]
Coordinates of the circumscribed circle: U[15; 4.375]
Coordinates of the inscribed circle: I[15; 7.5]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 126.8769897646° = 126°52'12″ = 0.9277295218 rad
∠ B' = β' = 126.8769897646° = 126°52'12″ = 0.9277295218 rad
∠ C' = γ' = 106.2660204708° = 106°15'37″ = 1.28770022176 rad

# How did we calculate this triangle?

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. ### 1. The triangle circumference is the sum of the lengths of its three sides ### 2. Semiperimeter of the triangle ### 3. The triangle area using Heron's formula ### 4. Calculate the heights of the triangle from its area. ### 5. Calculation of the inner angles of the triangle using a Law of Cosines    