# 18 25 28 triangle

### Acute scalene triangle.

Sides: a = 18   b = 25   c = 28

Area: T = 221.1866431546
Perimeter: p = 71
Semiperimeter: s = 35.5

Angle ∠ A = α = 39.1954967426° = 39°11'42″ = 0.68440812318 rad
Angle ∠ B = β = 61.36990101631° = 61°22'8″ = 1.0711091286 rad
Angle ∠ C = γ = 79.43660224109° = 79°26'10″ = 1.38664201358 rad

Height: ha = 24.57662701718
Height: hb = 17.69549145237
Height: hc = 15.79990308247

Median: ma = 24.97699819784
Median: mb = 19.94436706752
Median: mc = 16.68883192683

Inradius: r = 6.23106037055
Circumradius: R = 14.24113798983

Vertex coordinates: A[28; 0] B[0; 0] C[8.625; 15.79990308247]
Centroid: CG[12.20883333333; 5.26663436082]
Coordinates of the circumscribed circle: U[14; 2.6110919648]
Coordinates of the inscribed circle: I[10.5; 6.23106037055]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 140.8055032574° = 140°48'18″ = 0.68440812318 rad
∠ B' = β' = 118.6310989837° = 118°37'52″ = 1.0711091286 rad
∠ C' = γ' = 100.5643977589° = 100°33'50″ = 1.38664201358 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.