# 7 15 20 triangle

### Obtuse scalene triangle.

Sides: a = 7   b = 15   c = 20

Area: T = 42
Perimeter: p = 42
Semiperimeter: s = 21

Angle ∠ A = α = 16.26602047083° = 16°15'37″ = 0.28437941092 rad
Angle ∠ B = β = 36.87698976458° = 36°52'12″ = 0.64435011088 rad
Angle ∠ C = γ = 126.8769897646° = 126°52'12″ = 2.21442974356 rad

Height: ha = 12
Height: hb = 5.6
Height: hc = 4.2

Median: ma = 17.32877234512
Median: mb = 12.97111217711
Median: mc = 6.08327625303

Inradius: r = 2
Circumradius: R = 12.5

Vertex coordinates: A[20; 0] B[0; 0] C[5.6; 4.2]
Centroid: CG[8.53333333333; 1.4]
Coordinates of the circumscribed circle: U[10; -7.5]
Coordinates of the inscribed circle: I[6; 2]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 163.7439795292° = 163°44'23″ = 0.28437941092 rad
∠ B' = β' = 143.1330102354° = 143°7'48″ = 0.64435011088 rad
∠ C' = γ' = 53.13301023542° = 53°7'48″ = 2.21442974356 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.