# 2 20 21 triangle

### Obtuse scalene triangle.

Sides: a = 2   b = 20   c = 21

Area: T = 17.73223856263
Perimeter: p = 43
Semiperimeter: s = 21.5

Angle ∠ A = α = 4.84438195264° = 4°50'38″ = 0.08545405991 rad
Angle ∠ B = β = 57.60876345142° = 57°36'27″ = 1.00554428966 rad
Angle ∠ C = γ = 117.5498545959° = 117°32'55″ = 2.05216091579 rad

Height: ha = 17.73223856263
Height: hb = 1.77332385626
Height: hc = 1.68987986311

Median: ma = 20.48216991483
Median: mb = 11.06879718106
Median: mc = 9.57986220303

Inradius: r = 0.82547621222
Circumradius: R = 11.84327381643

Vertex coordinates: A[21; 0] B[0; 0] C[1.07114285714; 1.68987986311]
Centroid: CG[7.35771428571; 0.5632932877]
Coordinates of the circumscribed circle: U[10.5; -5.4777266401]
Coordinates of the inscribed circle: I[1.5; 0.82547621222]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 175.1566180474° = 175°9'22″ = 0.08545405991 rad
∠ B' = β' = 122.3922365486° = 122°23'33″ = 1.00554428966 rad
∠ C' = γ' = 62.45114540405° = 62°27'5″ = 2.05216091579 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.