# 20 26 26 triangle

### Acute isosceles triangle.

Sides: a = 20   b = 26   c = 26

Area: T = 240
Perimeter: p = 72
Semiperimeter: s = 36

Angle ∠ A = α = 45.24397298961° = 45°14'23″ = 0.79895822394 rad
Angle ∠ B = β = 67.3880135052° = 67°22'49″ = 1.17660052071 rad
Angle ∠ C = γ = 67.3880135052° = 67°22'49″ = 1.17660052071 rad

Height: ha = 24
Height: hb = 18.46215384615
Height: hc = 18.46215384615

Median: ma = 24
Median: mb = 19.20993727123
Median: mc = 19.20993727123

Inradius: r = 6.66766666667
Circumradius: R = 14.08333333333

Vertex coordinates: A[26; 0] B[0; 0] C[7.69223076923; 18.46215384615]
Centroid: CG[11.23107692308; 6.15438461538]
Coordinates of the circumscribed circle: U[13; 5.41766666667]
Coordinates of the inscribed circle: I[10; 6.66766666667]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 134.7660270104° = 134°45'37″ = 0.79895822394 rad
∠ B' = β' = 112.6219864948° = 112°37'11″ = 1.17660052071 rad
∠ C' = γ' = 112.6219864948° = 112°37'11″ = 1.17660052071 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    