# 12 15 20 triangle

### Obtuse scalene triangle.

Sides: a = 12   b = 15   c = 20

Area: T = 89.66656985697
Perimeter: p = 47
Semiperimeter: s = 23.5

Angle ∠ A = α = 36.71104466683° = 36°42'38″ = 0.64107181642 rad
Angle ∠ B = β = 48.35496321995° = 48°20'59″ = 0.8443860274 rad
Angle ∠ C = γ = 94.94399211322° = 94°56'24″ = 1.65770142153 rad

Height: ha = 14.9444283095
Height: hb = 11.9555426476
Height: hc = 8.9676569857

Median: ma = 16.62882891483
Median: mb = 14.68884308216
Median: mc = 9.19223881554

Inradius: r = 3.81655616413
Circumradius: R = 10.03772830899

Vertex coordinates: A[20; 0] B[0; 0] C[7.975; 8.9676569857]
Centroid: CG[9.325; 2.9898856619]
Coordinates of the circumscribed circle: U[10; -0.86443215994]
Coordinates of the inscribed circle: I[8.5; 3.81655616413]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 143.2989553332° = 143°17'22″ = 0.64107181642 rad
∠ B' = β' = 131.65503678° = 131°39'1″ = 0.8443860274 rad
∠ C' = γ' = 85.06600788678° = 85°3'36″ = 1.65770142153 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.