# 13 20 25 triangle

### Obtuse scalene triangle.

Sides: a = 13   b = 20   c = 25

Area: T = 129.2443955371
Perimeter: p = 58
Semiperimeter: s = 29

Angle ∠ A = α = 31.13296133228° = 31°7'47″ = 0.54333142474 rad
Angle ∠ B = β = 52.68880824408° = 52°41'17″ = 0.92195805152 rad
Angle ∠ C = γ = 96.18223042364° = 96°10'56″ = 1.67986978911 rad

Height: ha = 19.88436854417
Height: hb = 12.92443955371
Height: hc = 10.34395164297

Median: ma = 21.68552484422
Median: mb = 17.23436879396
Median: mc = 11.32547516529

Inradius: r = 4.45766881162
Circumradius: R = 12.57331218557

Vertex coordinates: A[25; 0] B[0; 0] C[7.88; 10.34395164297]
Centroid: CG[10.96; 3.44765054766]
Coordinates of the circumscribed circle: U[12.5; -1.35440285075]
Coordinates of the inscribed circle: I[9; 4.45766881162]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 148.8770386677° = 148°52'13″ = 0.54333142474 rad
∠ B' = β' = 127.3121917559° = 127°18'43″ = 0.92195805152 rad
∠ C' = γ' = 83.81876957636° = 83°49'4″ = 1.67986978911 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.