# 17 20 28 triangle

### Obtuse scalene triangle.

Sides: a = 17   b = 20   c = 28

Area: T = 168.3332817656
Perimeter: p = 65
Semiperimeter: s = 32.5

Angle ∠ A = α = 36.95550748363° = 36°57'18″ = 0.64549877312 rad
Angle ∠ B = β = 45.01440978737° = 45°51″ = 0.78656442177 rad
Angle ∠ C = γ = 98.03108272899° = 98°1'51″ = 1.71109607047 rad

Height: ha = 19.80438609007
Height: hb = 16.83332817656
Height: hc = 12.02437726897

Median: ma = 22.79880262304
Median: mb = 20.89325824158
Median: mc = 12.1866057607

Inradius: r = 5.17994713125
Circumradius: R = 14.13986571742

Vertex coordinates: A[28; 0] B[0; 0] C[12.01878571429; 12.02437726897]
Centroid: CG[13.33992857143; 4.00879242299]
Coordinates of the circumscribed circle: U[14; -1.97552535758]
Coordinates of the inscribed circle: I[12.5; 5.17994713125]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 143.0454925164° = 143°2'42″ = 0.64549877312 rad
∠ B' = β' = 134.9865902126° = 134°59'9″ = 0.78656442177 rad
∠ C' = γ' = 81.96991727101° = 81°58'9″ = 1.71109607047 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    