# 13 21 25 triangle

### Obtuse scalene triangle.

Sides: a = 13   b = 21   c = 25

Area: T = 136.4488479288
Perimeter: p = 59
Semiperimeter: s = 29.5

Angle ∠ A = α = 31.31990870573° = 31°19'9″ = 0.54766211879 rad
Angle ∠ B = β = 57.10766549978° = 57°6'24″ = 0.99766991545 rad
Angle ∠ C = γ = 91.57442579449° = 91°34'27″ = 1.59882723112 rad

Height: ha = 20.99220737366
Height: hb = 12.99550932655
Height: hc = 10.9165878343

Median: ma = 22.15328779169
Median: mb = 16.93436942219
Median: mc = 12.19663109177

Inradius: r = 4.62553721793
Circumradius: R = 12.50547197954

Vertex coordinates: A[25; 0] B[0; 0] C[7.06; 10.9165878343]
Centroid: CG[10.68766666667; 3.63986261143]
Coordinates of the circumscribed circle: U[12.5; -0.34435362581]
Coordinates of the inscribed circle: I[8.5; 4.62553721793]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 148.6810912943° = 148°40'51″ = 0.54766211879 rad
∠ B' = β' = 122.8933345002° = 122°53'36″ = 0.99766991545 rad
∠ C' = γ' = 88.42657420551° = 88°25'33″ = 1.59882723112 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.