Find the length of the circle circumscribed about a right-angled triangle with legs 15 cm and 20 cm.

The diameter of the circumscribed circle around a right-angled triangle coincides with the hypotenuse of the triangle. This is due to the fact that the right angle <C = 90 ° = 180 ° / 2, <180 always corresponds to the diameter of the circle.

Find the diameter d equal to c (hypotenuse).

c ^ 2 = a ^ 2 + b ^ 2, where a 15 cm and b = 20 cm are the legs of the triangle. c ^ 2 = 15 ^ 2 + 20 ^ 2 = 225 + 400 = 625 (cm ^ 2).

Then c = √625 = 25 (cm), whence d = c = 25 cm.

Circumference l = pi * d = 3.14 * 25 = 78.5 cm.

Answer: length l = 78.5 cm.