# 16 20 20 triangle

### Acute isosceles triangle.

Sides: a = 16   b = 20   c = 20

Area: T = 146.6422422239
Perimeter: p = 56
Semiperimeter: s = 28

Angle ∠ A = α = 47.15663569564° = 47°9'23″ = 0.82330336921 rad
Angle ∠ B = β = 66.42218215218° = 66°25'19″ = 1.15992794807 rad
Angle ∠ C = γ = 66.42218215218° = 66°25'19″ = 1.15992794807 rad

Height: ha = 18.33303027798
Height: hb = 14.66442422239
Height: hc = 14.66442422239

Median: ma = 18.33303027798
Median: mb = 15.10996688705
Median: mc = 15.10996688705

Inradius: r = 5.23772293657
Circumradius: R = 10.91108945118

Vertex coordinates: A[20; 0] B[0; 0] C[6.4; 14.66442422239]
Centroid: CG[8.8; 4.88880807413]
Coordinates of the circumscribed circle: U[10; 4.36443578047]
Coordinates of the inscribed circle: I[8; 5.23772293657]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 132.8443643044° = 132°50'37″ = 0.82330336921 rad
∠ B' = β' = 113.5788178478° = 113°34'41″ = 1.15992794807 rad
∠ C' = γ' = 113.5788178478° = 113°34'41″ = 1.15992794807 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    