# 7 7 9 triangle

### Acute isosceles triangle.

Sides: a = 7   b = 7   c = 9

Area: T = 24.12985619132
Perimeter: p = 23
Semiperimeter: s = 11.5

Angle ∠ A = α = 49.99547991151° = 49°59'41″ = 0.87325738534 rad
Angle ∠ B = β = 49.99547991151° = 49°59'41″ = 0.87325738534 rad
Angle ∠ C = γ = 80.01104017697° = 80°37″ = 1.39664449467 rad

Height: ha = 6.89438748323
Height: hb = 6.89438748323
Height: hc = 5.36219026474

Median: ma = 7.26329195232
Median: mb = 7.26329195232
Median: mc = 5.36219026474

Inradius: r = 2.09881358185
Circumradius: R = 4.56992735604

Vertex coordinates: A[9; 0] B[0; 0] C[4.5; 5.36219026474]
Centroid: CG[4.5; 1.78773008825]
Coordinates of the circumscribed circle: U[4.5; 0.7932629087]
Coordinates of the inscribed circle: I[4.5; 2.09881358185]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 130.0055200885° = 130°19″ = 0.87325738534 rad
∠ B' = β' = 130.0055200885° = 130°19″ = 0.87325738534 rad
∠ C' = γ' = 99.99895982303° = 99°59'23″ = 1.39664449467 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    