Asked by Laksh

x=2cosø-sinø and y=cosø-3sinø then prove that 2x+y-2xy=5
Steve
Hmmm.
2x+y-2xy = (4cosø-2sinø)+(cosø-3sinø)+(4cosø-2sinø)(cosø-3sinø)
= 5cosø-5sinø + 2sin^2ø+4-14sinøcosø

I don't get 5.

Typo?