# 12 21 25 triangle

### Obtuse scalene triangle.

Sides: a = 12   b = 21   c = 25

Area: T = 125.6032547745
Perimeter: p = 58
Semiperimeter: s = 29

Angle ∠ A = α = 28.58765601202° = 28°35'12″ = 0.49989295959 rad
Angle ∠ B = β = 56.86113684587° = 56°51'41″ = 0.99224180968 rad
Angle ∠ C = γ = 94.55220714212° = 94°33'7″ = 1.65502449609 rad

Height: ha = 20.93437579575
Height: hb = 11.96221474043
Height: hc = 10.04882038196

Median: ma = 22.29334968096
Median: mb = 16.56604951617
Median: mc = 11.67326175299

Inradius: r = 4.3311122336
Circumradius: R = 12.54395545574

Vertex coordinates: A[25; 0] B[0; 0] C[6.56; 10.04882038196]
Centroid: CG[10.52; 3.34994012732]
Coordinates of the circumscribed circle: U[12.5; -0.99552027427]
Coordinates of the inscribed circle: I[8; 4.3311122336]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 151.413343988° = 151°24'48″ = 0.49989295959 rad
∠ B' = β' = 123.1398631541° = 123°8'19″ = 0.99224180968 rad
∠ C' = γ' = 85.44879285788° = 85°26'53″ = 1.65502449609 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.