A ladder leaning against a vertical wall, makes an angle of 60

^{0}with the ground. The foot of the ladder is 3.5 m away from the wall. Find the length of the ladder.
Solution:

Let AC be
the length of the ladder,

AB be the
distance between the foot of the ladder and the base of the wall.

Thus, AB =
3.5 m (Given)

In right
angled triangle, ∆ ABC,

cos 60

^{0}=^{AB}/_{AC}_{}

∴

^{1}/_{2 }=^{3.5}/_{AC}
∴ AC = 3.5 × 2

∴ AC = 7 m.

∴ The length of the ladder is 7m.