Question
A ladder leaning against a wall makes an angle of 60° with the horizontal. If the foot of the ladder is 2.5 m away from the wall, find the length of the ladder.
Solution
Let AB be the ladder and CA be the wall.

∴ ΔABC is a 30o-60o-90o, right triangle.
Given: BC = 2.5 m, ∠ABC = 60°
AB = 5 cm and ∠BAC = 30°
From Pythagoras Theorem, we have
AB2 = BC2 + CA2
52 = (2.5)2 + (CA)2
(CA)2 = 25 – 6.25 = 18.75 m
Hence, length of the ladder is