Trigonometry
posted by fakku .
The angle of elevation of the sun is 20 degrees. At the same time,how long is the shadow cast by a building 50 meter high?

You would start off by setting up the equation as follows:
tan20=50/x (You would use tan because of the chief, SOHCAHTOA tan is opposite over adjacent.
multiply by x on both sides leaving you with
xtan20=50
Divide by tan 20.
Your answer would be 137.37 meters 
tan20=50/x
xtan20=50
50/tan20
137.37 meters