If a 20-foot ladder makes a 65° angle with the ground, how many feet up a wall will it reach? Round your answer to the nearest tenth.

We have an angle, a hypotenuse - the ladder length - and we're looking for the opposite side ... the sine seems the way to go, here ...

sin 65 = opp / 20 multiply both sides by 20

20 sin 65 = opp = about 18.13 ft up the wall