# 11 11 18 triangle

### Obtuse isosceles triangle.

Sides: a = 11   b = 11   c = 18

Area: T = 56.9210997883
Perimeter: p = 40
Semiperimeter: s = 20

Angle ∠ A = α = 35.09768012276° = 35°5'48″ = 0.61325547383 rad
Angle ∠ B = β = 35.09768012276° = 35°5'48″ = 0.61325547383 rad
Angle ∠ C = γ = 109.8066397545° = 109°48'23″ = 1.91664831769 rad

Height: ha = 10.34992723424
Height: hb = 10.34992723424
Height: hc = 6.32545553203

Median: ma = 13.86554246239
Median: mb = 13.86554246239
Median: mc = 6.32545553203

Inradius: r = 2.84660498942
Circumradius: R = 9.5665889922

Vertex coordinates: A[18; 0] B[0; 0] C[9; 6.32545553203]
Centroid: CG[9; 2.10881851068]
Coordinates of the circumscribed circle: U[9; -3.24113346017]
Coordinates of the inscribed circle: I[9; 2.84660498942]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 144.9033198772° = 144°54'12″ = 0.61325547383 rad
∠ B' = β' = 144.9033198772° = 144°54'12″ = 0.61325547383 rad
∠ C' = γ' = 70.19436024552° = 70°11'37″ = 1.91664831769 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.