Triangle calculator SSS - result

Please enter the triangle sides:

Acute scalene triangle.

Sides: a = 12   b = 18   c = 21

Area: T = 107.7898856103
Perimeter: p = 51
Semiperimeter: s = 25.5

Angle ∠ A = α = 34.77219440319° = 34°46'19″ = 0.60768849107 rad
Angle ∠ B = β = 58.81113776665° = 58°48'41″ = 1.02664521779 rad
Angle ∠ C = γ = 86.41766783015° = 86°25' = 1.5088255565 rad

Height: ha = 17.96548093505
Height: hb = 11.9776539567
Height: hc = 10.26656053431

Median: ma = 18.6154510469
Median: mb = 14.54330395722
Median: mc = 11.12442977306

Inradius: r = 4.22770139648
Circumradius: R = 10.52105680902

Vertex coordinates: A[21; 0] B[0; 0] C[6.21442857143; 10.26656053431]
Centroid: CG[9.07114285714; 3.42218684477]
Coordinates of the circumscribed circle: U[10.5; 0.65875355056]
Coordinates of the inscribed circle: I[7.5; 4.22770139648]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 145.2288055968° = 145°13'41″ = 0.60768849107 rad
∠ B' = β' = 121.1898622333° = 121°11'19″ = 1.02664521779 rad
∠ C' = γ' = 93.58333216985° = 93°35' = 1.5088255565 rad

How did we calculate this triangle?

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     