# 10 21 30 triangle

### Obtuse scalene triangle.

Sides: a = 10   b = 21   c = 30

Area: T = 54.49771329521
Perimeter: p = 61
Semiperimeter: s = 30.5

Angle ∠ A = α = 9.96326853346° = 9°57'46″ = 0.17438816614 rad
Angle ∠ B = β = 21.30438736689° = 21°18'14″ = 0.3721822739 rad
Angle ∠ C = γ = 148.7333440996° = 148°44' = 2.59658882532 rad

Height: ha = 10.89994265904
Height: hb = 5.19902031383
Height: hc = 3.63331421968

Median: ma = 25.40766920318
Median: mb = 19.74220870224
Median: mc = 6.74553687816

Inradius: r = 1.78767912443
Circumradius: R = 28.9010602925

Vertex coordinates: A[30; 0] B[0; 0] C[9.31766666667; 3.63331421968]
Centroid: CG[13.10655555556; 1.21110473989]
Coordinates of the circumscribed circle: U[15; -24.70331344049]
Coordinates of the inscribed circle: I[9.5; 1.78767912443]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 170.0377314665° = 170°2'14″ = 0.17438816614 rad
∠ B' = β' = 158.6966126331° = 158°41'46″ = 0.3721822739 rad
∠ C' = γ' = 31.26765590035° = 31°16' = 2.59658882532 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.