Forming thw diagram, you have the length of the hypotenuse, and you want to find the height, which is the 'opposite length to the angle'
So using SOHCAHTOA
we have:
sin15 = height / 3000
height = 3000 sin 15
height = 776.46m
So, the height of the plane above the ground at this instant is 776.46m
