# 17 20 21 triangle

### Acute scalene triangle.

Sides: a = 17   b = 20   c = 21

Area: T = 158.2910871499
Perimeter: p = 58
Semiperimeter: s = 29

Angle ∠ A = α = 48.91876668595° = 48°55'4″ = 0.85437743491 rad
Angle ∠ B = β = 62.47218164666° = 62°28'19″ = 1.0990338887 rad
Angle ∠ C = γ = 68.61105166738° = 68°36'38″ = 1.19774794175 rad

Height: ha = 18.62224554705
Height: hb = 15.82990871499
Height: hc = 15.07553210952

Median: ma = 18.66114576065
Median: mb = 16.27988205961
Median: mc = 15.3055227865

Inradius: r = 5.45883059138
Circumradius: R = 11.27767083982

Vertex coordinates: A[21; 0] B[0; 0] C[7.85771428571; 15.07553210952]
Centroid: CG[9.6199047619; 5.02551070317]
Coordinates of the circumscribed circle: U[10.5; 4.11326818864]
Coordinates of the inscribed circle: I[9; 5.45883059138]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 131.082233314° = 131°4'56″ = 0.85437743491 rad
∠ B' = β' = 117.5288183533° = 117°31'41″ = 1.0990338887 rad
∠ C' = γ' = 111.3899483326° = 111°23'22″ = 1.19774794175 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.