# 17 21 21 triangle

### Acute isosceles triangle.

Sides: a = 17   b = 21   c = 21

Area: T = 163.2244347142
Perimeter: p = 59
Semiperimeter: s = 29.5

Angle ∠ A = α = 47.75224154611° = 47°45'9″ = 0.83334368756 rad
Angle ∠ B = β = 66.12437922694° = 66°7'26″ = 1.1544077889 rad
Angle ∠ C = γ = 66.12437922694° = 66°7'26″ = 1.1544077889 rad

Height: ha = 19.20328643697
Height: hb = 15.54551759183
Height: hc = 15.54551759183

Median: ma = 19.20328643697
Median: mb = 15.96108896995
Median: mc = 15.96108896995

Inradius: r = 5.53330287167
Circumradius: R = 11.48326619485

Vertex coordinates: A[21; 0] B[0; 0] C[6.8810952381; 15.54551759183]
Centroid: CG[9.29436507937; 5.18217253061]
Coordinates of the circumscribed circle: U[10.5; 4.6487744122]
Coordinates of the inscribed circle: I[8.5; 5.53330287167]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 132.2487584539° = 132°14'51″ = 0.83334368756 rad
∠ B' = β' = 113.8766207731° = 113°52'34″ = 1.1544077889 rad
∠ C' = γ' = 113.8766207731° = 113°52'34″ = 1.1544077889 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.