# 11 20 21 triangle

### Acute scalene triangle.

Sides: a = 11   b = 20   c = 21

Area: T = 108.1676538264
Perimeter: p = 52
Semiperimeter: s = 26

Angle ∠ A = α = 31.00327191339° = 31°10″ = 0.5411099526 rad
Angle ∠ B = β = 69.47329625625° = 69°28'23″ = 1.21325319378 rad
Angle ∠ C = γ = 79.52443183036° = 79°31'28″ = 1.38879611898 rad

Height: ha = 19.66766433207
Height: hb = 10.81766538264
Height: hc = 10.30215750728

Median: ma = 19.75547462651
Median: mb = 13.45436240471
Median: mc = 12.25876506721

Inradius: r = 4.16602514717
Circumradius: R = 10.67879787773

Vertex coordinates: A[21; 0] B[0; 0] C[3.85771428571; 10.30215750728]
Centroid: CG[8.28657142857; 3.43438583576]
Coordinates of the circumscribed circle: U[10.5; 1.94114506868]
Coordinates of the inscribed circle: I[6; 4.16602514717]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 148.9977280866° = 148°59'50″ = 0.5411099526 rad
∠ B' = β' = 110.5277037437° = 110°31'37″ = 1.21325319378 rad
∠ C' = γ' = 100.4765681696° = 100°28'32″ = 1.38879611898 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.