# 13 18 28 triangle

### Obtuse scalene triangle.

Sides: a = 13   b = 18   c = 28

Area: T = 91.63220768072
Perimeter: p = 59
Semiperimeter: s = 29.5

Angle ∠ A = α = 21.3232639967° = 21°19'22″ = 0.37221502726 rad
Angle ∠ B = β = 30.23300357169° = 30°13'48″ = 0.52876136563 rad
Angle ∠ C = γ = 128.4477324316° = 128°26'50″ = 2.24218287247 rad

Height: ha = 14.09772425857
Height: hb = 10.18113418675
Height: hc = 6.54551483434

Median: ma = 22.62218920517
Median: mb = 19.88771818014
Median: mc = 7.10663352018

Inradius: r = 3.10661720952
Circumradius: R = 17.87658362472

Vertex coordinates: A[28; 0] B[0; 0] C[11.23221428571; 6.54551483434]
Centroid: CG[13.07773809524; 2.18217161145]
Coordinates of the circumscribed circle: U[14; -11.11551033076]
Coordinates of the inscribed circle: I[11.5; 3.10661720952]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 158.6777360033° = 158°40'38″ = 0.37221502726 rad
∠ B' = β' = 149.7769964283° = 149°46'12″ = 0.52876136563 rad
∠ C' = γ' = 51.5532675684° = 51°33'10″ = 2.24218287247 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.