# 18 20 30 triangle

### Obtuse scalene triangle.

Sides: a = 18   b = 20   c = 30

Area: T = 174.5399393834
Perimeter: p = 68
Semiperimeter: s = 34

Angle ∠ A = α = 35.57771025511° = 35°34'38″ = 0.62109375778 rad
Angle ∠ B = β = 40.274389294° = 40°16'26″ = 0.70329120344 rad
Angle ∠ C = γ = 104.1499004509° = 104°8'56″ = 1.81877430414 rad

Height: ha = 19.39332659816
Height: hb = 17.45439393834
Height: hc = 11.63659595889

Median: ma = 23.85437208838
Median: mb = 22.6277416998
Median: mc = 11.70546999107

Inradius: r = 5.13435115834
Circumradius: R = 15.46992871374

Vertex coordinates: A[30; 0] B[0; 0] C[13.73333333333; 11.63659595889]
Centroid: CG[14.57877777778; 3.87986531963]
Coordinates of the circumscribed circle: U[15; -3.78113813002]
Coordinates of the inscribed circle: I[14; 5.13435115834]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 144.4232897449° = 144°25'22″ = 0.62109375778 rad
∠ B' = β' = 139.726610706° = 139°43'34″ = 0.70329120344 rad
∠ C' = γ' = 75.85109954911° = 75°51'4″ = 1.81877430414 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.