The identity can be rewritten as:
which is always true.
arent i suppose to use the left hand side only, and prove it is equal to the right hand side?
hahaha. i'm stuck with the number 1. guessed i'm supposed to use the cos2+sin2=1 formula to get rid of it, but do not know how. or maybe i;m wrong, there other way. (Nerd)
thank you great_math.
took me an hour to come up with those lines this morning. but mine is way longer.. (Whew)