# 13 13 18 triangle

### Acute isosceles triangle.

Sides: a = 13   b = 13   c = 18

Area: T = 84.42774836768
Perimeter: p = 44
Semiperimeter: s = 22

Angle ∠ A = α = 46.18769385396° = 46°11'13″ = 0.80661141489 rad
Angle ∠ B = β = 46.18769385396° = 46°11'13″ = 0.80661141489 rad
Angle ∠ C = γ = 87.62661229208° = 87°37'34″ = 1.52993643557 rad

Height: ha = 12.98988436426
Height: hb = 12.98988436426
Height: hc = 9.38108315196

Median: ma = 14.2921605928
Median: mb = 14.2921605928
Median: mc = 9.38108315196

Inradius: r = 3.83876128944
Circumradius: R = 9.0087730266

Vertex coordinates: A[18; 0] B[0; 0] C[9; 9.38108315196]
Centroid: CG[9; 3.12769438399]
Coordinates of the circumscribed circle: U[9; 0.37331012536]
Coordinates of the inscribed circle: I[9; 3.83876128944]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 133.813306146° = 133°48'47″ = 0.80661141489 rad
∠ B' = β' = 133.813306146° = 133°48'47″ = 0.80661141489 rad
∠ C' = γ' = 92.37438770792° = 92°22'26″ = 1.52993643557 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.