# 2 7 8 triangle

### Obtuse scalene triangle.

Sides: a = 2   b = 7   c = 8

Area: T = 6.43771965948
Perimeter: p = 17
Semiperimeter: s = 8.5

Angle ∠ A = α = 13.2911177243° = 13°17'28″ = 0.23219748044 rad
Angle ∠ B = β = 53.57664263577° = 53°34'35″ = 0.93550850414 rad
Angle ∠ C = γ = 113.1322396399° = 113°7'57″ = 1.97545328078 rad

Height: ha = 6.43771965948
Height: hb = 1.83991990271
Height: hc = 1.60992991487

Median: ma = 7.45498322129
Median: mb = 4.66436895265
Median: mc = 3.24403703492

Inradius: r = 0.75773172464
Circumradius: R = 4.35497195693

Vertex coordinates: A[8; 0] B[0; 0] C[1.18875; 1.60992991487]
Centroid: CG[3.06325; 0.53664330496]
Coordinates of the circumscribed circle: U[4; -1.70988184022]
Coordinates of the inscribed circle: I[1.5; 0.75773172464]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 166.7098822757° = 166°42'32″ = 0.23219748044 rad
∠ B' = β' = 126.4243573642° = 126°25'25″ = 0.93550850414 rad
∠ C' = γ' = 66.86876036007° = 66°52'3″ = 1.97545328078 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    