# 11 12 21 triangle

### Obtuse scalene triangle.

Sides: a = 11   b = 12   c = 21

Area: T = 49.1933495505
Perimeter: p = 44
Semiperimeter: s = 22

Angle ∠ A = α = 22.98109198075° = 22°58'51″ = 0.40110927158 rad
Angle ∠ B = β = 25.20987652968° = 25°12'32″ = 0.44399759548 rad
Angle ∠ C = γ = 131.8110314896° = 131°48'37″ = 2.3010523983 rad

Height: ha = 8.944427191
Height: hb = 8.19989159175
Height: hc = 4.685509481

Median: ma = 16.19441347407
Median: mb = 15.65224758425
Median: mc = 4.7176990566

Inradius: r = 2.23660679775
Circumradius: R = 14.08772282582

Vertex coordinates: A[21; 0] B[0; 0] C[9.95223809524; 4.685509481]
Centroid: CG[10.31774603175; 1.562169827]
Coordinates of the circumscribed circle: U[10.5; -9.39114855055]
Coordinates of the inscribed circle: I[10; 2.23660679775]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 157.0199080193° = 157°1'9″ = 0.40110927158 rad
∠ B' = β' = 154.7911234703° = 154°47'28″ = 0.44399759548 rad
∠ C' = γ' = 48.19896851042° = 48°11'23″ = 2.3010523983 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.