# 5 18 18 triangle

### Acute isosceles triangle.

Sides: a = 5   b = 18   c = 18

Area: T = 44.56438586749
Perimeter: p = 41
Semiperimeter: s = 20.5

Angle ∠ A = α = 15.96771122911° = 15°58'2″ = 0.27986786815 rad
Angle ∠ B = β = 82.01664438544° = 82°59″ = 1.4311456986 rad
Angle ∠ C = γ = 82.01664438544° = 82°59″ = 1.4311456986 rad

Height: ha = 17.826554347
Height: hb = 4.95215398528
Height: hc = 4.95215398528

Median: ma = 17.826554347
Median: mb = 9.67695398029
Median: mc = 9.67695398029

Inradius: r = 2.17438467646
Circumradius: R = 9.08880819579

Vertex coordinates: A[18; 0] B[0; 0] C[0.69444444444; 4.95215398528]
Centroid: CG[6.23114814815; 1.65105132843]
Coordinates of the circumscribed circle: U[9; 1.26222336053]
Coordinates of the inscribed circle: I[2.5; 2.17438467646]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 164.0332887709° = 164°1'58″ = 0.27986786815 rad
∠ B' = β' = 97.98435561456° = 97°59'1″ = 1.4311456986 rad
∠ C' = γ' = 97.98435561456° = 97°59'1″ = 1.4311456986 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.