# 16 18 18 triangle

### Acute isosceles triangle.

Sides: a = 16   b = 18   c = 18

Area: T = 128.9966123973
Perimeter: p = 52
Semiperimeter: s = 26

Angle ∠ A = α = 52.77655999225° = 52°46'32″ = 0.92111079834 rad
Angle ∠ B = β = 63.61222000388° = 63°36'44″ = 1.11102423351 rad
Angle ∠ C = γ = 63.61222000388° = 63°36'44″ = 1.11102423351 rad

Height: ha = 16.12545154966
Height: hb = 14.33329026636
Height: hc = 14.33329026636

Median: ma = 16.12545154966
Median: mb = 14.45768322948
Median: mc = 14.45768322948

Inradius: r = 4.96113893836
Circumradius: R = 10.04768135017

Vertex coordinates: A[18; 0] B[0; 0] C[7.11111111111; 14.33329026636]
Centroid: CG[8.37703703704; 4.77876342212]
Coordinates of the circumscribed circle: U[9; 4.46552504452]
Coordinates of the inscribed circle: I[8; 4.96113893836]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 127.2244400078° = 127°13'28″ = 0.92111079834 rad
∠ B' = β' = 116.3887799961° = 116°23'16″ = 1.11102423351 rad
∠ C' = γ' = 116.3887799961° = 116°23'16″ = 1.11102423351 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    