# 21 21 26 triangle

### Acute isosceles triangle.

Sides: a = 21   b = 21   c = 26

Area: T = 214.4011492532
Perimeter: p = 68
Semiperimeter: s = 34

Angle ∠ A = α = 51.75333801217° = 51°45'12″ = 0.90332668822 rad
Angle ∠ B = β = 51.75333801217° = 51°45'12″ = 0.90332668822 rad
Angle ∠ C = γ = 76.49332397567° = 76°29'36″ = 1.33550588893 rad

Height: ha = 20.4199189765
Height: hb = 20.4199189765
Height: hc = 16.49224225025

Median: ma = 21.17219153597
Median: mb = 21.17219153597
Median: mc = 16.49224225025

Inradius: r = 6.30659262509
Circumradius: R = 13.37697763301

Vertex coordinates: A[26; 0] B[0; 0] C[13; 16.49224225025]
Centroid: CG[13; 5.49774741675]
Coordinates of the circumscribed circle: U[13; 3.12326461723]
Coordinates of the inscribed circle: I[13; 6.30659262509]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 128.2476619878° = 128°14'48″ = 0.90332668822 rad
∠ B' = β' = 128.2476619878° = 128°14'48″ = 0.90332668822 rad
∠ C' = γ' = 103.5076760243° = 103°30'24″ = 1.33550588893 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.