# 18 30 30 triangle

### Acute isosceles triangle.

Sides: a = 18   b = 30   c = 30

Area: T = 257.5643584383
Perimeter: p = 78
Semiperimeter: s = 39

Angle ∠ A = α = 34.91552062474° = 34°54'55″ = 0.6099385308 rad
Angle ∠ B = β = 72.54223968763° = 72°32'33″ = 1.26661036728 rad
Angle ∠ C = γ = 72.54223968763° = 72°32'33″ = 1.26661036728 rad

Height: ha = 28.61881760425
Height: hb = 17.17109056255
Height: hc = 17.17109056255

Median: ma = 28.61881760425
Median: mb = 19.67223155729
Median: mc = 19.67223155729

Inradius: r = 6.60441944713
Circumradius: R = 15.72442725508

Vertex coordinates: A[30; 0] B[0; 0] C[5.4; 17.17109056255]
Centroid: CG[11.8; 5.72436352085]
Coordinates of the circumscribed circle: U[15; 4.71772817652]
Coordinates of the inscribed circle: I[9; 6.60441944713]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 145.0854793753° = 145°5'5″ = 0.6099385308 rad
∠ B' = β' = 107.4587603124° = 107°27'27″ = 1.26661036728 rad
∠ C' = γ' = 107.4587603124° = 107°27'27″ = 1.26661036728 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.