In a Δ ABC, B = 90°, AB = 24cm and BC = 7cm. Find

a) sinA


b) cosA


c) sinC


d) cosC

Clearly Δ ABC is a right angled triangle,



By Pythagoras theorem, (hypotenuse)2 = (perpendicular)2 + (base)2


AC2 = BC2 + AB2


= AC2 = (7)2 + (24)2


= AC2 = 49 + 576


= AC2 = 625


AC = 25


a) sinA = BC/AC = 7/25


b) cosA = AB/AC = 24/25


c) sinC = AB/AC = 24/25


d) cosC = BC/AC = 7/25


25