A ladder 15 m long just reaches the top of a vertical wall. If the ladder makes an angle of 60° with the wall, then the height of the wall is:
Answer: C
Be careful with the angle. The angle is with the *wall*, not the ground.
Let h be the height of the wall (adjacent side to the 60° angle) and L be the length of the ladder (hypotenuse).
\(\cos(\text{angle}) = \frac{\text{Adjacent}}{\text{Hypotenuse}}\)
\(\cos 60° = \frac{h}{15}\)
\(\frac{1}{2} = \frac{h}{15}\)
h = 15 / 2 = 7.5 meters.