# 13 18 30 triangle

### Obtuse scalene triangle.

Sides: a = 13   b = 18   c = 30

Area: T = 57.75875752607
Perimeter: p = 61
Semiperimeter: s = 30.5

Angle ∠ A = α = 12.35219946365° = 12°21'7″ = 0.21655829756 rad
Angle ∠ B = β = 17.22990702856° = 17°13'45″ = 0.30107040035 rad
Angle ∠ C = γ = 150.4198935078° = 150°25'8″ = 2.62553056745 rad

Height: ha = 8.88657808093
Height: hb = 6.41875083623
Height: hc = 3.85105050174

Median: ma = 23.86994365246
Median: mb = 21.2965539439
Median: mc = 4.63768092477

Inradius: r = 1.89436909922
Circumradius: R = 30.38656246056

Vertex coordinates: A[30; 0] B[0; 0] C[12.41766666667; 3.85105050174]
Centroid: CG[14.13988888889; 1.28435016725]
Coordinates of the circumscribed circle: U[15; -26.42551051591]
Coordinates of the inscribed circle: I[12.5; 1.89436909922]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 167.6488005363° = 167°38'53″ = 0.21655829756 rad
∠ B' = β' = 162.7710929714° = 162°46'15″ = 0.30107040035 rad
∠ C' = γ' = 29.58110649222° = 29°34'52″ = 2.62553056745 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    