# 2 21 21 triangle

### Acute isosceles triangle.

Sides: a = 2   b = 21   c = 21

Area: T = 20.97661769634
Perimeter: p = 44
Semiperimeter: s = 22

Angle ∠ A = α = 5.45988052736° = 5°27'32″ = 0.09552741252 rad
Angle ∠ B = β = 87.27105973632° = 87°16'14″ = 1.52331592642 rad
Angle ∠ C = γ = 87.27105973632° = 87°16'14″ = 1.52331592642 rad

Height: ha = 20.97661769634
Height: hb = 1.99877311394
Height: hc = 1.99877311394

Median: ma = 20.97661769634
Median: mb = 10.59548100502
Median: mc = 10.59548100502

Inradius: r = 0.95334625892
Circumradius: R = 10.51219250464

Vertex coordinates: A[21; 0] B[0; 0] C[0.09552380952; 1.99877311394]
Centroid: CG[7.03217460317; 0.66659103798]
Coordinates of the circumscribed circle: U[10.5; 0.50105678594]
Coordinates of the inscribed circle: I[1; 0.95334625892]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 174.5411194726° = 174°32'28″ = 0.09552741252 rad
∠ B' = β' = 92.72994026368° = 92°43'46″ = 1.52331592642 rad
∠ C' = γ' = 92.72994026368° = 92°43'46″ = 1.52331592642 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.