In a right-angled triangle ABC c = 90 degrees b = 60 degrees AB = 15 cm, find BC.

A right-angled triangle is a triangle in which one of the angles is 90 °.

To calculate the length of the side BC, we use the cosine theorem. The cosine of an acute angle of a right-angled triangle is the ratio of the adjacent leg to the hypotenuse:

cos B = BC / AB;

cos 60º = 1/2;

ВС = AB ∙ cos B;

BC = 15 ∙ 1/2 = 15/2 = 7.5 cm.

Answer: The length of the BC side is 7.5 cm.