# 18 20 25 triangle

### Acute scalene triangle.

Sides: a = 18   b = 20   c = 25

Area: T = 178.2990318021
Perimeter: p = 63
Semiperimeter: s = 31.5

Angle ∠ A = α = 45.49327106983° = 45°29'34″ = 0.79439975873 rad
Angle ∠ B = β = 52.41104970351° = 52°24'38″ = 0.91547357359 rad
Angle ∠ C = γ = 82.09767922665° = 82°5'48″ = 1.43328593304 rad

Height: ha = 19.81100353357
Height: hb = 17.82990318021
Height: hc = 14.26332254417

Median: ma = 20.77325780778
Median: mb = 19.35220024804
Median: mc = 14.34439882878

Inradius: r = 5.66600100959
Circumradius: R = 12.62198664346

Vertex coordinates: A[25; 0] B[0; 0] C[10.98; 14.26332254417]
Centroid: CG[11.99333333333; 4.75444084806]
Coordinates of the circumscribed circle: U[12.5; 1.73552316348]
Coordinates of the inscribed circle: I[11.5; 5.66600100959]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 134.5077289302° = 134°30'26″ = 0.79439975873 rad
∠ B' = β' = 127.5989502965° = 127°35'22″ = 0.91547357359 rad
∠ C' = γ' = 97.90332077335° = 97°54'12″ = 1.43328593304 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.