# 4 12 15 triangle

### Obtuse scalene triangle.

Sides: a = 4   b = 12   c = 15

Area: T = 17.66217524612
Perimeter: p = 31
Semiperimeter: s = 15.5

Angle ∠ A = α = 11.31772690307° = 11°19'2″ = 0.19875236069 rad
Angle ∠ B = β = 36.06765882598° = 36°4' = 0.62994807151 rad
Angle ∠ C = γ = 132.6166142709° = 132°36'58″ = 2.31545883316 rad

Height: ha = 8.83108762306
Height: hb = 2.94436254102
Height: hc = 2.35549003282

Median: ma = 13.43550288425
Median: mb = 9.19223881554
Median: mc = 4.87333971724

Inradius: r = 1.13994679007
Circumradius: R = 10.19215141431

Vertex coordinates: A[15; 0] B[0; 0] C[3.23333333333; 2.35549003282]
Centroid: CG[6.07877777778; 0.78549667761]
Coordinates of the circumscribed circle: U[7.5; -6.90105043677]
Coordinates of the inscribed circle: I[3.5; 1.13994679007]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 168.6832730969° = 168°40'58″ = 0.19875236069 rad
∠ B' = β' = 143.933341174° = 143°56' = 0.62994807151 rad
∠ C' = γ' = 47.38438572905° = 47°23'2″ = 2.31545883316 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.