A ladder 10 m long just reaches the top of a wall and makes an angle of 60° with the wall.Find the distance of the foot of the ladder from the wall ( 3 = 1.73 )

Answer: Option D

Let BA be the ladder and AC be the wall as shown above.
Then the distance of the foot of the ladder from the wall = BC
Given that BA = 10 m, ∠ BAC = 60°
$$\begin{array}{rl}& \sin 60^{\circ }=\frac{BC}{BA}\\ & \frac{\sqrt{3}}{2}=\frac{BC}{10}\\ & BC=10\times \frac{\sqrt{3}}{2}\\ & =5\times 1.73\\ & =8.65\text{m}\end{array}$$