# 20 28 28 triangle

### Acute isosceles triangle.

Sides: a = 20   b = 28   c = 28

Area: T = 261.5343936612
Perimeter: p = 76
Semiperimeter: s = 38

Angle ∠ A = α = 41.85496648553° = 41°50'59″ = 0.73304144426 rad
Angle ∠ B = β = 69.07551675724° = 69°4'31″ = 1.20655891055 rad
Angle ∠ C = γ = 69.07551675724° = 69°4'31″ = 1.20655891055 rad

Height: ha = 26.15333936612
Height: hb = 18.68109954723
Height: hc = 18.68109954723

Median: ma = 26.15333936612
Median: mb = 19.98997487421
Median: mc = 19.98997487421

Inradius: r = 6.88224720161
Circumradius: R = 14.98884946129

Vertex coordinates: A[28; 0] B[0; 0] C[7.14328571429; 18.68109954723]
Centroid: CG[11.71442857143; 6.22769984908]
Coordinates of the circumscribed circle: U[14; 5.35330337903]
Coordinates of the inscribed circle: I[10; 6.88224720161]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 138.1550335145° = 138°9'1″ = 0.73304144426 rad
∠ B' = β' = 110.9254832428° = 110°55'29″ = 1.20655891055 rad
∠ C' = γ' = 110.9254832428° = 110°55'29″ = 1.20655891055 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 ### 6. Inradius ### 7. Circumradius ### 8. Calculation of medians #### Look also our friend's collection of math examples and problems:

See more informations about triangles or more information about solving triangles.