6 18 18 triangle

Acute isosceles triangle.

Sides: a = 6   b = 18   c = 18

Area: T = 53.24547180479
Perimeter: p = 42
Semiperimeter: s = 21

Angle ∠ A = α = 19.18881364537° = 19°11'17″ = 0.33548961584 rad
Angle ∠ B = β = 80.40659317731° = 80°24'21″ = 1.40333482476 rad
Angle ∠ C = γ = 80.40659317731° = 80°24'21″ = 1.40333482476 rad

Height: ha = 17.74882393493
Height: hb = 5.91660797831
Height: hc = 5.91660797831

Median: ma = 17.74882393493
Median: mb = 9.95498743711
Median: mc = 9.95498743711

Vertex coordinates: A[18; 0] B[0; 0] C[1; 5.91660797831]
Centroid: CG[6.33333333333; 1.97220265944]
Coordinates of the circumscribed circle: U[9; 1.52112776585]
Coordinates of the inscribed circle: I[3; 2.53554627642]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 160.8121863546° = 160°48'43″ = 0.33548961584 rad
∠ B' = β' = 99.59440682269° = 99°35'39″ = 1.40333482476 rad
∠ C' = γ' = 99.59440682269° = 99°35'39″ = 1.40333482476 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    