# 13 18 20 triangle

### Acute scalene triangle.

Sides: a = 13   b = 18   c = 20

Area: T = 114.6676636386
Perimeter: p = 51
Semiperimeter: s = 25.5

Angle ∠ A = α = 39.57112194572° = 39°34'16″ = 0.69106480686 rad
Angle ∠ B = β = 61.89107787174° = 61°53'27″ = 1.08801978652 rad
Angle ∠ C = γ = 78.53880018254° = 78°32'17″ = 1.37107467198 rad

Height: ha = 17.64110209824
Height: hb = 12.74107373762
Height: hc = 11.46766636386

Median: ma = 17.88215547422
Median: mb = 14.26553426177
Median: mc = 12.10437184369

Inradius: r = 4.49767308387
Circumradius: R = 10.20334910666

Vertex coordinates: A[20; 0] B[0; 0] C[6.125; 11.46766636386]
Centroid: CG[8.70883333333; 3.82222212129]
Coordinates of the circumscribed circle: U[10; 2.02876168145]
Coordinates of the inscribed circle: I[7.5; 4.49767308387]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 140.4298780543° = 140°25'44″ = 0.69106480686 rad
∠ B' = β' = 118.1099221283° = 118°6'33″ = 1.08801978652 rad
∠ C' = γ' = 101.4621998175° = 101°27'43″ = 1.37107467198 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.