If a 30 m ladder is placed against a 15 m wall such that it just reaches the top of the wall, then the elevation of the wall is equal to-

Answer: Option B

Solution

Answer: Option B

Solution:

$$\begin{array}{rl}& \text{AC = 30 meter}\\ & \text{AB = 15 meter}\\ & \angle \text{ACB}=\theta \\ & \therefore \sin \theta =\frac{AB}{AC}=\frac{15}{30}=\frac{1}{2}\\ & \Rightarrow \sin \theta =\sin 30^{\circ }\\ & \Rightarrow \theta =30^{\circ }\end{array}$$