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 Question from Kristine, a student: Find measure of unknown side cosA=0.5

Hi Kristine,

Suppose you have a right triangle. The side opposite the right angle is called the hypotenuse. Let A is one of the angles, not the right angle. The other two sides are given names relative to A. The side close to A is called the adjacent side and the third side is called the side opposite to A.

The cosine of the angle A is defined to be the length of the adjacent side divided by the length of the hypotenuse, so