# 3 7 8 triangle

### Obtuse scalene triangle.

Sides: a = 3   b = 7   c = 8

Area: T = 10.39223048454
Perimeter: p = 18
Semiperimeter: s = 9

Angle ∠ A = α = 21.78767892983° = 21°47'12″ = 0.38802512067 rad
Angle ∠ B = β = 60° = 1.04771975512 rad
Angle ∠ C = γ = 98.21332107017° = 98°12'48″ = 1.71441438957 rad

Height: ha = 6.92882032303
Height: hb = 2.96992299558
Height: hc = 2.59880762114

Median: ma = 7.36554599313
Median: mb = 4.92444289009
Median: mc = 3.60655512755

Inradius: r = 1.15547005384
Circumradius: R = 4.04114518843

Vertex coordinates: A[8; 0] B[0; 0] C[1.5; 2.59880762114]
Centroid: CG[3.16766666667; 0.86660254038]
Coordinates of the circumscribed circle: U[4; -0.57773502692]
Coordinates of the inscribed circle: I[2; 1.15547005384]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 158.2133210702° = 158°12'48″ = 0.38802512067 rad
∠ B' = β' = 120° = 1.04771975512 rad
∠ C' = γ' = 81.78767892983° = 81°47'12″ = 1.71441438957 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    