The ABC triangle is acute-angled. AB = BC = 26, AC = 20. Find the area and radii of the inscribed and circumscribed circles.

1) find the semiperimeter
p = (26 + 26 + 20) / 2 = 36
2) find the area of the triangle by Heron’s formula
S = √36 * (36-26) ^ 2 * (36-20) = 240
3) R inscribed env = √ (p-a) ^ 2 * (p-b) / p
Substitute numbers (a = 26, b = 20, p = 36)
R inscribed = 20/3 = 6 whole 2/3
4) R describe env = (a ^ 2 * b) / (4 * S)
Substituting numbers
R description = 676/48 = 14 whole 1/12