# 15 15 18 triangle

### Acute isosceles triangle.

Sides: a = 15   b = 15   c = 18

Area: T = 108
Perimeter: p = 48
Semiperimeter: s = 24

Angle ∠ A = α = 53.13301023542° = 53°7'48″ = 0.9277295218 rad
Angle ∠ B = β = 53.13301023542° = 53°7'48″ = 0.9277295218 rad
Angle ∠ C = γ = 73.74397952917° = 73°44'23″ = 1.28770022176 rad

Height: ha = 14.4
Height: hb = 14.4
Height: hc = 12

Median: ma = 14.77332867027
Median: mb = 14.77332867027
Median: mc = 12

Inradius: r = 4.5
Circumradius: R = 9.375

Vertex coordinates: A[18; 0] B[0; 0] C[9; 12]
Centroid: CG[9; 4]
Coordinates of the circumscribed circle: U[9; 2.625]
Coordinates of the inscribed circle: I[9; 4.5]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 126.8769897646° = 126°52'12″ = 0.9277295218 rad
∠ B' = β' = 126.8769897646° = 126°52'12″ = 0.9277295218 rad
∠ C' = γ' = 106.2660204708° = 106°15'37″ = 1.28770022176 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.