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