Remark
The function that relates the side opposite to the hypotenuse is
Sin(x) = opposite / hypotenuse
Givens
x = 9
opposite = 3
hypotenuse = y
Solve
sin(9) = 3/y Multiply both sides by y
y*sin(9) = 3 Divide by Sin(9)
y = 3/Sin(9)
y = 3/0.1564
y = 19.18
So the length of the hypotenuse (ramp) is 19.18 feet