# 9 9 17 triangle

### Obtuse isosceles triangle.

Sides: a = 9   b = 9   c = 17

Area: T = 25.14333390782
Perimeter: p = 35
Semiperimeter: s = 17.5

Angle ∠ A = α = 19.18881364537° = 19°11'17″ = 0.33548961584 rad
Angle ∠ B = β = 19.18881364537° = 19°11'17″ = 0.33548961584 rad
Angle ∠ C = γ = 141.6243727093° = 141°37'25″ = 2.47218003367 rad

Height: ha = 5.5877408684
Height: hb = 5.5877408684
Height: hc = 2.95880398915

Median: ma = 12.8355497653
Median: mb = 12.8355497653
Median: mc = 2.95880398915

Inradius: r = 1.4376762233
Circumradius: R = 13.69114989266

Vertex coordinates: A[17; 0] B[0; 0] C[8.5; 2.95880398915]
Centroid: CG[8.5; 0.98660132972]
Coordinates of the circumscribed circle: U[8.5; -10.73334590351]
Coordinates of the inscribed circle: I[8.5; 1.4376762233]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 160.8121863546° = 160°48'43″ = 0.33548961584 rad
∠ B' = β' = 160.8121863546° = 160°48'43″ = 0.33548961584 rad
∠ C' = γ' = 38.37662729074° = 38°22'35″ = 2.47218003367 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    