Right-angled triangle ABC has angle C = 90 °, side AB = 25cm, side BC = 20cm, find the cos of angle B and tg A.

According to the Pythagorean theorem, the side AC of a right-angled triangle ABC is equal to the square root of the difference between the squares of the sides AB and BC, that is

AC = (25 ^ 2 – 20 ^ 2) ^ 0.5 = (625 – 400) ^ 0.5 = 225 ^ 0.5 = 15 cm.

cos of angle B is equal to the ratio of side BC to side AB:

BC / AB = 20/25 = 0.8.

tg A is equal to the ratio of the aircraft side to the AC side:

BC / AC = 20/15 = 4/3 = 1.333.