a We have been given the angle and hypotenuse, and we want to determine the opposite leg labeled x. Given this information, we have to use the sine ratio to calculate x.
b We have been given the angle and opposite leg and want to determine the adjacent leg labeled x. Given this information, we have to use the tangent ratio to calculate x.
c We have been given the hypotenuse and adjacent leg to an unknown angle labeled θ. Given this information, we have to use the cosine ratio to calculate θ.