Look up (and learn) the expansion rules for sin(a+b), cos(a+b), tan(a+b), sin (a-b),
sin2a, etc. And apply them here. Have a go or you'll never never know.
Hello Johnny Walker Black
1) Use the identities below to expand the LHS:Simplify the result. Then take out a common factor of . Then use:
and you're done.
2) Use the identities:Simplify the result, and factorise. Then use:
in the numerator. Simplify; cancel, and you're there.
3) Get rid of and (horrible things!) by multiplying top-and-bottom of the fraction by , using the fact that:andThen use:Simplify. Then use , and you're there.