The leg of a right-angled triangle is 15 cm, and the hypotenuse is 25 cm. Calculate the length of the second leg.

1. By the Pythagorean theorem: in a right-angled triangle, the square of the hypotenuse is equal to the sum of the squares of the legs. Hypotenuse – BC = 25 cm, legs behind AB and AC = 15 cm. Looking for length AB. The hypotenuse is the largest side, therefore, to calculate its length, you need to add the squares of the legs. To calculate the length of the leg, you need to subtract the square of the known leg from the square of the hypotenuse.
2.BC ^ 2 = AB ^ 2 + AC ^ 2. 25 ^ 2 = AB ^ 2 + 15 ^ 2. 625 = AB ^ 2 + 225.625 – 225 = AB ^ 2. 400 = AB ^ 2. AB = 20 cm.
Answer: AB = 20 cm.