# 12 13 18 triangle

### Obtuse scalene triangle.

Sides: a = 12   b = 13   c = 18

Area: T = 77.95215073619
Perimeter: p = 43
Semiperimeter: s = 21.5

Angle ∠ A = α = 41.77884625885° = 41°46'42″ = 0.72991717286 rad
Angle ∠ B = β = 46.20110751782° = 46°12'4″ = 0.80663608798 rad
Angle ∠ C = γ = 92.02204622333° = 92°1'14″ = 1.60660600452 rad

Height: ha = 12.99219178937
Height: hb = 11.99325395941
Height: hc = 8.66112785958

Median: ma = 14.50986181285
Median: mb = 13.84773824241
Median: mc = 8.68990735985

Inradius: r = 3.62656515052
Circumradius: R = 9.00655987852

Vertex coordinates: A[18; 0] B[0; 0] C[8.30655555556; 8.66112785958]
Centroid: CG[8.76985185185; 2.88770928653]
Coordinates of the circumscribed circle: U[9; -0.31875050854]
Coordinates of the inscribed circle: I[8.5; 3.62656515052]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 138.2221537411° = 138°13'18″ = 0.72991717286 rad
∠ B' = β' = 133.7998924822° = 133°47'56″ = 0.80663608798 rad
∠ C' = γ' = 87.98795377667° = 87°58'46″ = 1.60660600452 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.