# 18 26 30 triangle

### Acute scalene triangle.

Sides: a = 18   b = 26   c = 30

Area: T = 232.6610697154
Perimeter: p = 74
Semiperimeter: s = 37

Angle ∠ A = α = 36.62443415398° = 36°37'28″ = 0.63992153462 rad
Angle ∠ B = β = 59.50987077655° = 59°30'31″ = 1.03986228841 rad
Angle ∠ C = γ = 83.86769506947° = 83°52'1″ = 1.46437544232 rad

Height: ha = 25.85111885726
Height: hb = 17.89769767041
Height: hc = 15.51107131436

Median: ma = 26.58994716006
Median: mb = 21.04875651798
Median: mc = 16.58331239518

Inradius: r = 6.28881269501
Circumradius: R = 15.08663469548

Vertex coordinates: A[30; 0] B[0; 0] C[9.13333333333; 15.51107131436]
Centroid: CG[13.04444444444; 5.17702377145]
Coordinates of the circumscribed circle: U[15; 1.61217892046]
Coordinates of the inscribed circle: I[11; 6.28881269501]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 143.376565846° = 143°22'32″ = 0.63992153462 rad
∠ B' = β' = 120.4911292234° = 120°29'29″ = 1.03986228841 rad
∠ C' = γ' = 96.13330493053° = 96°7'59″ = 1.46437544232 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    