# 15 21 30 triangle

### Obtuse scalene triangle.

Sides: a = 15   b = 21   c = 30

Area: T = 146.2332691283
Perimeter: p = 66
Semiperimeter: s = 33

Angle ∠ A = α = 27.66604498993° = 27°39'38″ = 0.48327659233 rad
Angle ∠ B = β = 40.53658021113° = 40°32'9″ = 0.70774832118 rad
Angle ∠ C = γ = 111.8043747989° = 111°48'13″ = 1.95113435185 rad

Height: ha = 19.49876921711
Height: hb = 13.92769229794
Height: hc = 9.74988460856

Median: ma = 24.78440674628
Median: mb = 21.26661703181
Median: mc = 10.39223048454

Inradius: r = 4.43112936753
Circumradius: R = 16.1565758191

Vertex coordinates: A[30; 0] B[0; 0] C[11.4; 9.74988460856]
Centroid: CG[13.8; 3.25496153619]
Coordinates of the circumscribed circle: U[15; -6.00107101852]
Coordinates of the inscribed circle: I[12; 4.43112936753]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 152.3439550101° = 152°20'22″ = 0.48327659233 rad
∠ B' = β' = 139.4644197889° = 139°27'51″ = 0.70774832118 rad
∠ C' = γ' = 68.19662520106° = 68°11'47″ = 1.95113435185 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.