For this case we use the following definition: sine (x) = (C.O) / (h) Where, x: angle C.O: opposite leg h: hypotenuse Substituting values: sine (C) = (C.O) / (h) sine (C) = (AB) / (82) We look for AB by Pythagorean theorem: AB = root ((82) ^ 2 - (80) ^ 2) AB = 18 Substituting: sine (C) = (18) / (82) Simplifying: sine (C) = (9) / (41) Answer: the ratio is: sine (C) = (9) / (41)