<P> A right triangle (American English) or right - angled triangle (British English) is a triangle in which one angle is a right angle (that is, a 90 - degree angle). The relation between the sides and angles of a right triangle is the basis for trigonometry . </P> <P> The side opposite the right angle is called the hypotenuse (side c in the figure). The sides adjacent to the right angle are called legs (or catheti, singular: cathetus). Side a may be identified as the side adjacent to angle B and opposed to (or opposite) angle A, while side b is the side adjacent to angle A and opposed to angle B . </P> <P> If the lengths of all three sides of a right triangle are integers, the triangle is said to be a Pythagorean triangle and its side lengths are collectively known as a Pythagorean triple . </P>

What is the opposite side of a right angle triangle