Trigonometric ratios

Question

If a 20 ft ladder places against a house reaches a height of 18ft on the wall, what’s the measure of the angle that the ladder makes with the ground?

Answer 1

Solution:

The 20 ft ladder gets placed at an angle to the house is actually the Hypotenuse of the right angle triangle with vertical side = 18 ft.

The sine of the angle a that the ladder makes with the wall is:

sin(a) = opposite/hypotenuse = 18/20 = 0.9, the inverse of the value that is the angle a

a= sin^-1(sin(a))= sin^-1(0.9)= 64.15°