# 13 16 21 triangle

### Obtuse scalene triangle.

Sides: a = 13   b = 16   c = 21

Area: T = 103.9233048454
Perimeter: p = 50
Semiperimeter: s = 25

Angle ∠ A = α = 38.21332107017° = 38°12'48″ = 0.66769463445 rad
Angle ∠ B = β = 49.58325617943° = 49°34'57″ = 0.86553789549 rad
Angle ∠ C = γ = 92.2044227504° = 92°12'15″ = 1.60992673542 rad

Height: ha = 15.98881613006
Height: hb = 12.99903810568
Height: hc = 9.89774331861

Median: ma = 17.5
Median: mb = 15.52441746963
Median: mc = 10.11218742081

Inradius: r = 4.15769219382
Circumradius: R = 10.50877748993

Vertex coordinates: A[21; 0] B[0; 0] C[8.42985714286; 9.89774331861]
Centroid: CG[9.81095238095; 3.29991443954]
Coordinates of the circumscribed circle: U[10.5; -0.40441451884]
Coordinates of the inscribed circle: I[9; 4.15769219382]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 141.7876789298° = 141°47'12″ = 0.66769463445 rad
∠ B' = β' = 130.4177438206° = 130°25'3″ = 0.86553789549 rad
∠ C' = γ' = 87.7965772496° = 87°47'45″ = 1.60992673542 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.