# 16 20 25 triangle

### Acute scalene triangle.

Sides: a = 16   b = 20   c = 25

Area: T = 159.8122194466
Perimeter: p = 61
Semiperimeter: s = 30.5

Angle ∠ A = α = 39.73658255397° = 39°44'9″ = 0.69435209867 rad
Angle ∠ B = β = 53.04105251447° = 53°2'26″ = 0.92657318008 rad
Angle ∠ C = γ = 87.22436493156° = 87°13'25″ = 1.52223398662 rad

Height: ha = 19.97765243082
Height: hb = 15.98112194466
Height: hc = 12.78549755573

Median: ma = 21.17878185845
Median: mb = 18.45326420872
Median: mc = 13.10553424221

Inradius: r = 5.24397440808
Circumradius: R = 12.51546895497

Vertex coordinates: A[25; 0] B[0; 0] C[9.62; 12.78549755573]
Centroid: CG[11.54; 4.26216585191]
Coordinates of the circumscribed circle: U[12.5; 0.60661802751]
Coordinates of the inscribed circle: I[10.5; 5.24397440808]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 140.264417446° = 140°15'51″ = 0.69435209867 rad
∠ B' = β' = 126.9599474855° = 126°57'34″ = 0.92657318008 rad
∠ C' = γ' = 92.77663506844° = 92°46'35″ = 1.52223398662 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    