# 18 20 20 triangle

### Acute isosceles triangle.

Sides: a = 18   b = 20   c = 20

Area: T = 160.7455139895
Perimeter: p = 58
Semiperimeter: s = 29

Angle ∠ A = α = 53.48773679008° = 53°29'15″ = 0.93435306781 rad
Angle ∠ B = β = 63.25663160496° = 63°15'23″ = 1.10440309877 rad
Angle ∠ C = γ = 63.25663160496° = 63°15'23″ = 1.10440309877 rad

Height: ha = 17.86105710995
Height: hb = 16.07545139895
Height: hc = 16.07545139895

Median: ma = 17.86105710995
Median: mb = 16.18664140562
Median: mc = 16.18664140562

Inradius: r = 5.54329358585
Circumradius: R = 11.19878502191

Vertex coordinates: A[20; 0] B[0; 0] C[8.1; 16.07545139895]
Centroid: CG[9.36766666667; 5.35881713298]
Coordinates of the circumscribed circle: U[10; 5.03990325986]
Coordinates of the inscribed circle: I[9; 5.54329358585]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 126.5132632099° = 126°30'45″ = 0.93435306781 rad
∠ B' = β' = 116.744368395° = 116°44'37″ = 1.10440309877 rad
∠ C' = γ' = 116.744368395° = 116°44'37″ = 1.10440309877 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.