# 12 15 18 triangle

### Acute scalene triangle.

Sides: a = 12   b = 15   c = 18

Area: T = 89.29441067484
Perimeter: p = 45
Semiperimeter: s = 22.5

Angle ∠ A = α = 41.41096221093° = 41°24'35″ = 0.72327342478 rad
Angle ∠ B = β = 55.77111336722° = 55°46'16″ = 0.97333899101 rad
Angle ∠ C = γ = 82.81992442185° = 82°49'9″ = 1.44554684956 rad

Height: ha = 14.88223511247
Height: hb = 11.90658808998
Height: hc = 9.92215674165

Median: ma = 15.44334452115
Median: mb = 13.3322291626
Median: mc = 10.17334949747

Inradius: r = 3.96986269666
Circumradius: R = 9.07111473522

Vertex coordinates: A[18; 0] B[0; 0] C[6.75; 9.92215674165]
Centroid: CG[8.25; 3.30771891388]
Coordinates of the circumscribed circle: U[9; 1.1343893419]
Coordinates of the inscribed circle: I[7.5; 3.96986269666]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 138.5990377891° = 138°35'25″ = 0.72327342478 rad
∠ B' = β' = 124.2298866328° = 124°13'44″ = 0.97333899101 rad
∠ C' = γ' = 97.18107557815° = 97°10'51″ = 1.44554684956 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.