# 18.2 17.1 12.3 triangle

### Acute scalene triangle.

Sides: a = 18.2   b = 17.1   c = 12.3

Area: T = 101.3377179752
Perimeter: p = 47.6
Semiperimeter: s = 23.8

Angle ∠ A = α = 74.49438507276° = 74°29'38″ = 1.33001629677 rad
Angle ∠ B = β = 64.87220959542° = 64°52'20″ = 1.13222316671 rad
Angle ∠ C = γ = 40.63440533182° = 40°38'3″ = 0.70991980188 rad

Height: ha = 11.13659538189
Height: hb = 11.85223017253
Height: hc = 16.47875902035

Median: ma = 11.79215223784
Median: mb = 12.96877484553
Median: mc = 16.55330208723

Inradius: r = 4.25878646954
Circumradius: R = 9.4443735284

Vertex coordinates: A[12.3; 0] B[0; 0] C[7.72884552846; 16.47875902035]
Centroid: CG[6.67661517615; 5.49325300678]
Coordinates of the circumscribed circle: U[6.15; 7.16767032947]
Coordinates of the inscribed circle: I[6.7; 4.25878646954]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 105.5066149272° = 105°30'22″ = 1.33001629677 rad
∠ B' = β' = 115.1287904046° = 115°7'40″ = 1.13222316671 rad
∠ C' = γ' = 139.3665946682° = 139°21'57″ = 0.70991980188 rad

# How did we calculate this triangle?

### 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    