# 12 18 18 triangle

### Acute isosceles triangle.

Sides: a = 12   b = 18   c = 18

Area: T = 101.8233376491
Perimeter: p = 48
Semiperimeter: s = 24

Angle ∠ A = α = 38.9422441269° = 38°56'33″ = 0.68796738189 rad
Angle ∠ B = β = 70.52987793655° = 70°31'44″ = 1.23109594173 rad
Angle ∠ C = γ = 70.52987793655° = 70°31'44″ = 1.23109594173 rad

Height: ha = 16.97105627485
Height: hb = 11.3143708499
Height: hc = 11.3143708499

Median: ma = 16.97105627485
Median: mb = 12.36993168769
Median: mc = 12.36993168769

Inradius: r = 4.24326406871
Circumradius: R = 9.5465941546

Vertex coordinates: A[18; 0] B[0; 0] C[4; 11.3143708499]
Centroid: CG[7.33333333333; 3.77112361663]
Coordinates of the circumscribed circle: U[9; 3.18219805153]
Coordinates of the inscribed circle: I[6; 4.24326406871]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 141.0587558731° = 141°3'27″ = 0.68796738189 rad
∠ B' = β' = 109.4711220634° = 109°28'16″ = 1.23109594173 rad
∠ C' = γ' = 109.4711220634° = 109°28'16″ = 1.23109594173 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.