then the ratio of opposite side/hypotenuse =5/13 By Pythagorean Theorem If opposite side =5units and hypotenuse =13 units
(for any units) then adjacent side=12 units and cos=adjacent side over hypotenuse =12/13
However, we need to note that if the angle is in Quadrant II then the adjacent side will actually be a negative value so cos= 12/13 for an angle in Q1 or cos= -12/13 for an angle in Q2 (angle can’t be in Q3 or Q4, since sin > 0)
