# 12 16 21 triangle

### Obtuse scalene triangle.

Sides: a = 12   b = 16   c = 21

Area: T = 95.45112310031
Perimeter: p = 49
Semiperimeter: s = 24.5

Angle ∠ A = α = 34.62221618397° = 34°37'20″ = 0.60442707183 rad
Angle ∠ B = β = 49.24986367043° = 49°14'55″ = 0.86595508626 rad
Angle ∠ C = γ = 96.12992014559° = 96°7'45″ = 1.67877710727 rad

Height: ha = 15.90985385005
Height: hb = 11.93114038754
Height: hc = 9.09105934289

Median: ma = 17.67876695297
Median: mb = 15.11662164578
Median: mc = 9.47436476607

Inradius: r = 3.89659686124
Circumradius: R = 10.56603666858

Vertex coordinates: A[21; 0] B[0; 0] C[7.83333333333; 9.09105934289]
Centroid: CG[9.61111111111; 3.03301978096]
Coordinates of the circumscribed circle: U[10.5; -1.12875391513]
Coordinates of the inscribed circle: I[8.5; 3.89659686124]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 145.378783816° = 145°22'40″ = 0.60442707183 rad
∠ B' = β' = 130.7511363296° = 130°45'5″ = 0.86595508626 rad
∠ C' = γ' = 83.87107985441° = 83°52'15″ = 1.67877710727 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.