# 16 21 25 triangle

### Acute scalene triangle.

Sides: a = 16   b = 21   c = 25

Area: T = 167.0332930885
Perimeter: p = 62
Semiperimeter: s = 31

Angle ∠ A = α = 39.51876527972° = 39°31'4″ = 0.6989713154 rad
Angle ∠ B = β = 56.63329870308° = 56°37'59″ = 0.98884320889 rad
Angle ∠ C = γ = 83.84993601721° = 83°50'58″ = 1.46334474107 rad

Height: ha = 20.87991163606
Height: hb = 15.90878981795
Height: hc = 13.36326344708

Median: ma = 21.65664078277
Median: mb = 18.17327818454
Median: mc = 13.86554246239

Inradius: r = 5.38881590608
Circumradius: R = 12.57223711419

Vertex coordinates: A[25; 0] B[0; 0] C[8.8; 13.36326344708]
Centroid: CG[11.26766666667; 4.45442114903]
Coordinates of the circumscribed circle: U[12.5; 1.34770397652]
Coordinates of the inscribed circle: I[10; 5.38881590608]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 140.4822347203° = 140°28'56″ = 0.6989713154 rad
∠ B' = β' = 123.3677012969° = 123°22'1″ = 0.98884320889 rad
∠ C' = γ' = 96.15106398279° = 96°9'2″ = 1.46334474107 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    