# 17 17 21 triangle

### Acute isosceles triangle.

Sides: a = 17   b = 17   c = 21

Area: T = 140.382229055
Perimeter: p = 55
Semiperimeter: s = 27.5

Angle ∠ A = α = 51.85554868988° = 51°51'20″ = 0.90550489816 rad
Angle ∠ B = β = 51.85554868988° = 51°51'20″ = 0.90550489816 rad
Angle ∠ C = γ = 76.28990262025° = 76°17'21″ = 1.33114946904 rad

Height: ha = 16.51655635941
Height: hb = 16.51655635941
Height: hc = 13.37697419571

Median: ma = 17.11099386323
Median: mb = 17.11099386323
Median: mc = 13.37697419571

Inradius: r = 5.10548105654
Circumradius: R = 10.80879872045

Vertex coordinates: A[21; 0] B[0; 0] C[10.5; 13.37697419571]
Centroid: CG[10.5; 4.45765806524]
Coordinates of the circumscribed circle: U[10.5; 2.56217547526]
Coordinates of the inscribed circle: I[10.5; 5.10548105654]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 128.1454513101° = 128°8'40″ = 0.90550489816 rad
∠ B' = β' = 128.1454513101° = 128°8'40″ = 0.90550489816 rad
∠ C' = γ' = 103.7110973798° = 103°42'39″ = 1.33114946904 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.