# 7 18 18 triangle

### Acute isosceles triangle.

Sides: a = 7   b = 18   c = 18

Area: T = 61.79875525405
Perimeter: p = 43
Semiperimeter: s = 21.5

Angle ∠ A = α = 22.42545428353° = 22°25'28″ = 0.39113821057 rad
Angle ∠ B = β = 78.78877285824° = 78°47'16″ = 1.37551052739 rad
Angle ∠ C = γ = 78.78877285824° = 78°47'16″ = 1.37551052739 rad

Height: ha = 17.6566443583
Height: hb = 6.86663947267
Height: hc = 6.86663947267

Median: ma = 17.6566443583
Median: mb = 10.27113192921
Median: mc = 10.27113192921

Inradius: r = 2.87443047693
Circumradius: R = 9.1755120643

Vertex coordinates: A[18; 0] B[0; 0] C[1.36111111111; 6.86663947267]
Centroid: CG[6.45437037037; 2.28987982422]
Coordinates of the circumscribed circle: U[9; 1.78440512361]
Coordinates of the inscribed circle: I[3.5; 2.87443047693]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 157.5755457165° = 157°34'32″ = 0.39113821057 rad
∠ B' = β' = 101.2122271418° = 101°12'44″ = 1.37551052739 rad
∠ C' = γ' = 101.2122271418° = 101°12'44″ = 1.37551052739 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.