# 12 20 30 triangle

### Obtuse scalene triangle.

Sides: a = 12   b = 20   c = 30

Area: T = 80.49222356504
Perimeter: p = 62
Semiperimeter: s = 31

Angle ∠ A = α = 15.56435751871° = 15°33'49″ = 0.27216356304 rad
Angle ∠ B = β = 26.56328406278° = 26°33'46″ = 0.46436090276 rad
Angle ∠ C = γ = 137.8743584185° = 137°52'25″ = 2.40663479956 rad

Height: ha = 13.41553726084
Height: hb = 8.0499223565
Height: hc = 5.36661490434

Median: ma = 24.77990233867
Median: mb = 20.54326385842
Median: mc = 6.85656546004

Inradius: r = 2.59765237307
Circumradius: R = 22.36224053358

Vertex coordinates: A[30; 0] B[0; 0] C[10.73333333333; 5.36661490434]
Centroid: CG[13.57877777778; 1.78987163478]
Coordinates of the circumscribed circle: U[15; -16.58554506241]
Coordinates of the inscribed circle: I[11; 2.59765237307]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 164.4366424813° = 164°26'11″ = 0.27216356304 rad
∠ B' = β' = 153.4377159372° = 153°26'14″ = 0.46436090276 rad
∠ C' = γ' = 42.12664158149° = 42°7'35″ = 2.40663479956 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.