# 15 16 21 triangle

### Acute scalene triangle.

Sides: a = 15   b = 16   c = 21

Area: T = 119.5832607431
Perimeter: p = 52
Semiperimeter: s = 26

Angle ∠ A = α = 45.38216583472° = 45°22'54″ = 0.79220593582 rad
Angle ∠ B = β = 49.39985335° = 49°23'55″ = 0.86221670552 rad
Angle ∠ C = γ = 85.22198081528° = 85°13'11″ = 1.48773662402 rad

Height: ha = 15.94443476575
Height: hb = 14.94878259289
Height: hc = 11.38988197553

Median: ma = 17.09553209973
Median: mb = 16.40112194669
Median: mc = 11.41327122105

Inradius: r = 4.5999331055
Circumradius: R = 10.53766493261

Vertex coordinates: A[21; 0] B[0; 0] C[9.76219047619; 11.38988197553]
Centroid: CG[10.2543968254; 3.79662732518]
Coordinates of the circumscribed circle: U[10.5; 0.87880541105]
Coordinates of the inscribed circle: I[10; 4.5999331055]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 134.6188341653° = 134°37'6″ = 0.79220593582 rad
∠ B' = β' = 130.60114665° = 130°36'5″ = 0.86221670552 rad
∠ C' = γ' = 94.78801918472° = 94°46'49″ = 1.48773662402 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.