# 20 21 30 triangle

### Obtuse scalene triangle.

Sides: a = 20   b = 21   c = 30

Area: T = 209.4811353585
Perimeter: p = 71
Semiperimeter: s = 35.5

Angle ∠ A = α = 41.68438728078° = 41°41'2″ = 0.72875208255 rad
Angle ∠ B = β = 44.28884644613° = 44°17'18″ = 0.77329795255 rad
Angle ∠ C = γ = 94.02876627308° = 94°1'40″ = 1.64110923026 rad

Height: ha = 20.94881353585
Height: hb = 19.95106051034
Height: hc = 13.96554235724

Median: ma = 23.8855141825
Median: mb = 23.2332520311
Median: mc = 13.98221314541

Inradius: r = 5.90108831996
Circumradius: R = 15.03771378936

Vertex coordinates: A[30; 0] B[0; 0] C[14.31766666667; 13.96554235724]
Centroid: CG[14.77222222222; 4.65551411908]
Coordinates of the circumscribed circle: U[15; -1.05661799235]
Coordinates of the inscribed circle: I[14.5; 5.90108831996]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 138.3166127192° = 138°18'58″ = 0.72875208255 rad
∠ B' = β' = 135.7121535539° = 135°42'42″ = 0.77329795255 rad
∠ C' = γ' = 85.97223372692° = 85°58'20″ = 1.64110923026 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.