# 9 20 20 triangle

### Acute isosceles triangle.

Sides: a = 9   b = 20   c = 20

Area: T = 87.69222887146
Perimeter: p = 49
Semiperimeter: s = 24.5

Angle ∠ A = α = 26.00657563258° = 26°21″ = 0.45438860724 rad
Angle ∠ B = β = 76.99771218371° = 76°59'50″ = 1.34438532906 rad
Angle ∠ C = γ = 76.99771218371° = 76°59'50″ = 1.34438532906 rad

Height: ha = 19.48771752699
Height: hb = 8.76992288715
Height: hc = 8.76992288715

Median: ma = 19.48771752699
Median: mb = 11.85332695911
Median: mc = 11.85332695911

Inradius: r = 3.57992770904
Circumradius: R = 10.26331601158

Vertex coordinates: A[20; 0] B[0; 0] C[2.025; 8.76992288715]
Centroid: CG[7.34216666667; 2.92330762905]
Coordinates of the circumscribed circle: U[10; 2.30992110261]
Coordinates of the inscribed circle: I[4.5; 3.57992770904]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 153.9944243674° = 153°59'39″ = 0.45438860724 rad
∠ B' = β' = 103.0032878163° = 103°10″ = 1.34438532906 rad
∠ C' = γ' = 103.0032878163° = 103°10″ = 1.34438532906 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.