How high is a 40-foot ramp if it is propped at a 30 degree angle?

This is the concept of trigonometry, the height of the ramp will be given by:
sin theta=[opposite]/[hypotenuse]
theta=30
opposite=x
hypotenuse=40 ft
hence;
sin 30=x/40
thus;
x=40sin30
x=20 ft
the ramp is 20 ft high