21 28 28 triangle

Acute isosceles triangle.

Sides: a = 21   b = 28   c = 28

Area: T = 272.5455294401
Perimeter: p = 77
Semiperimeter: s = 38.5

Angle ∠ A = α = 44.04986256741° = 44°2'55″ = 0.7698793549 rad
Angle ∠ B = β = 67.9765687163° = 67°58'32″ = 1.18663995523 rad
Angle ∠ C = γ = 67.9765687163° = 67°58'32″ = 1.18663995523 rad

Height: ha = 25.95766947048
Height: hb = 19.46875210286
Height: hc = 19.46875210286

Median: ma = 25.95766947048
Median: mb = 20.4088331632
Median: mc = 20.4088331632

Vertex coordinates: A[28; 0] B[0; 0] C[7.875; 19.46875210286]
Centroid: CG[11.95883333333; 6.48991736762]
Coordinates of the circumscribed circle: U[14; 5.66332788447]
Coordinates of the inscribed circle: I[10.5; 7.07990985559]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 135.9511374326° = 135°57'5″ = 0.7698793549 rad
∠ B' = β' = 112.0244312837° = 112°1'28″ = 1.18663995523 rad
∠ C' = γ' = 112.0244312837° = 112°1'28″ = 1.18663995523 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    