# 13 20 28 triangle

### Obtuse scalene triangle.

Sides: a = 13   b = 20   c = 28

Area: T = 118.3687806012
Perimeter: p = 61
Semiperimeter: s = 30.5

Angle ∠ A = α = 25.00878332347° = 25°28″ = 0.43664690287 rad
Angle ∠ B = β = 40.57696972304° = 40°34'11″ = 0.70880747932 rad
Angle ∠ C = γ = 114.4222469535° = 114°25'21″ = 1.99770488316 rad

Height: ha = 18.21104316941
Height: hb = 11.83767806012
Height: hc = 8.45548432865

Median: ma = 23.44767481754
Median: mb = 19.40436079119
Median: mc = 9.40774438611

Inradius: r = 3.88109116725
Circumradius: R = 15.37658024359

Vertex coordinates: A[28; 0] B[0; 0] C[9.875; 8.45548432865]
Centroid: CG[12.625; 2.81882810955]
Coordinates of the circumscribed circle: U[14; -6.35773029302]
Coordinates of the inscribed circle: I[10.5; 3.88109116725]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 154.9922166765° = 154°59'32″ = 0.43664690287 rad
∠ B' = β' = 139.433030277° = 139°25'49″ = 0.70880747932 rad
∠ C' = γ' = 65.5787530465° = 65°34'39″ = 1.99770488316 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.