# 10 21 21 triangle

### Acute isosceles triangle.

Sides: a = 10   b = 21   c = 21

Area: T = 101.9880390272
Perimeter: p = 52
Semiperimeter: s = 26

Angle ∠ A = α = 27.54882939961° = 27°32'54″ = 0.48108084335 rad
Angle ∠ B = β = 76.2265853002° = 76°13'33″ = 1.333039211 rad
Angle ∠ C = γ = 76.2265853002° = 76°13'33″ = 1.333039211 rad

Height: ha = 20.39660780544
Height: hb = 9.71224181211
Height: hc = 9.71224181211

Median: ma = 20.39660780544
Median: mb = 12.65989889012
Median: mc = 12.65989889012

Inradius: r = 3.92223227028
Circumradius: R = 10.81109019495

Vertex coordinates: A[21; 0] B[0; 0] C[2.3810952381; 9.71224181211]
Centroid: CG[7.79436507937; 3.2377472707]
Coordinates of the circumscribed circle: U[10.5; 2.57440242737]
Coordinates of the inscribed circle: I[5; 3.92223227028]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 152.4521706004° = 152°27'6″ = 0.48108084335 rad
∠ B' = β' = 103.7744146998° = 103°46'27″ = 1.333039211 rad
∠ C' = γ' = 103.7744146998° = 103°46'27″ = 1.333039211 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.