# 7 15 21 triangle

### Obtuse scalene triangle.

Sides: a = 7   b = 15   c = 21

Area: T = 31.83106063404
Perimeter: p = 43
Semiperimeter: s = 21.5

Angle ∠ A = α = 11.66597348859° = 11°39'35″ = 0.20435007637 rad
Angle ∠ B = β = 25.66325149891° = 25°39'45″ = 0.44878953809 rad
Angle ∠ C = γ = 142.6787750125° = 142°40'40″ = 2.4990196509 rad

Height: ha = 9.09444589544
Height: hb = 4.24440808454
Height: hc = 3.03114863181

Median: ma = 17.90994946886
Median: mb = 13.7398631664
Median: mc = 5.17220402164

Inradius: r = 1.48804933182
Circumradius: R = 17.31882374883

Vertex coordinates: A[21; 0] B[0; 0] C[6.31095238095; 3.03114863181]
Centroid: CG[9.10331746032; 1.01104954394]
Coordinates of the circumscribed circle: U[10.5; -13.77221221931]
Coordinates of the inscribed circle: I[6.5; 1.48804933182]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 168.3440265114° = 168°20'25″ = 0.20435007637 rad
∠ B' = β' = 154.3377485011° = 154°20'15″ = 0.44878953809 rad
∠ C' = γ' = 37.3222249875° = 37°19'20″ = 2.4990196509 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.