# 21 21 24 triangle

### Acute isosceles triangle.

Sides: a = 21   b = 21   c = 24

Area: T = 206.8044255275
Perimeter: p = 66
Semiperimeter: s = 33

Angle ∠ A = α = 55.1550095421° = 55°9' = 0.96325507479 rad
Angle ∠ B = β = 55.1550095421° = 55°9' = 0.96325507479 rad
Angle ∠ C = γ = 69.76998091581° = 69°41'59″ = 1.21664911578 rad

Height: ha = 19.69656433596
Height: hb = 19.69656433596
Height: hc = 17.23436879396

Median: ma = 19.95662020435
Median: mb = 19.95662020435
Median: mc = 17.23436879396

Inradius: r = 6.26767956144
Circumradius: R = 12.79547077127

Vertex coordinates: A[24; 0] B[0; 0] C[12; 17.23436879396]
Centroid: CG[12; 5.74545626465]
Coordinates of the circumscribed circle: U[12; 4.43989802269]
Coordinates of the inscribed circle: I[12; 6.26767956144]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 124.8549904579° = 124°51' = 0.96325507479 rad
∠ B' = β' = 124.8549904579° = 124°51' = 0.96325507479 rad
∠ C' = γ' = 110.3300190842° = 110°18'1″ = 1.21664911578 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.