# 9 16 18 triangle

### Acute scalene triangle.

Sides: a = 9   b = 16   c = 18

Area: T = 71.92766119041
Perimeter: p = 43
Semiperimeter: s = 21.5

Angle ∠ A = α = 29.96662882425° = 29°57'59″ = 0.52330103944 rad
Angle ∠ B = β = 62.62108586508° = 62°37'15″ = 1.09329401639 rad
Angle ∠ C = γ = 87.41328531068° = 87°24'46″ = 1.52656420953 rad

Height: ha = 15.98436915342
Height: hb = 8.9910826488
Height: hc = 7.99218457671

Median: ma = 16.42440677057
Median: mb = 11.76986022959
Median: mc = 9.35441434669

Inradius: r = 3.34554238095
Circumradius: R = 9.00991828719

Vertex coordinates: A[18; 0] B[0; 0] C[4.13988888889; 7.99218457671]
Centroid: CG[7.38796296296; 2.6643948589]
Coordinates of the circumscribed circle: U[9; 0.40766645046]
Coordinates of the inscribed circle: I[5.5; 3.34554238095]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 150.0343711758° = 150°2'1″ = 0.52330103944 rad
∠ B' = β' = 117.3799141349° = 117°22'45″ = 1.09329401639 rad
∠ C' = γ' = 92.58771468932° = 92°35'14″ = 1.52656420953 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    