# 11 12 18 triangle

### Obtuse scalene triangle.

Sides: a = 11   b = 12   c = 18

Area: T = 64.3310688633
Perimeter: p = 41
Semiperimeter: s = 20.5

Angle ∠ A = α = 36.55993057341° = 36°33'34″ = 0.63880802573 rad
Angle ∠ B = β = 40.5276896475° = 40°31'37″ = 0.70773277791 rad
Angle ∠ C = γ = 102.9143797791° = 102°54'50″ = 1.79661846172 rad

Height: ha = 11.69664888424
Height: hb = 10.72217814388
Height: hc = 7.14878542926

Median: ma = 14.27441024236
Median: mb = 13.65765002837
Median: mc = 7.17663500472

Inradius: r = 3.13880823723
Circumradius: R = 9.23435402064

Vertex coordinates: A[18; 0] B[0; 0] C[8.36111111111; 7.14878542926]
Centroid: CG[8.7877037037; 2.38326180975]
Coordinates of the circumscribed circle: U[9; -2.0643556334]
Coordinates of the inscribed circle: I[8.5; 3.13880823723]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 143.4410694266° = 143°26'26″ = 0.63880802573 rad
∠ B' = β' = 139.4733103525° = 139°28'23″ = 0.70773277791 rad
∠ C' = γ' = 77.08662022091° = 77°5'10″ = 1.79661846172 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.