Answer, 32.23°.
Suppose the setpoint of a helicopter is A and that of a car is C and that of the road is B
The distance from the helicopter to the car and the road forms a right triangle
=> ΔABC is a right triangle at B
=> the angle of depression from the helicopter from the car is ∠ACB
we have: ΔABC is a right triangle => sin ∠ACB = 24/45
=> m∠ACB = 32.23°