Verify these: [i need help getting started and other help you can throw at me]
1) sin(x + y)cos y - cos (x + y)sin y = sin x
2) cot x = (cos3x + cos x) / (sin 3x - sin x)
3) tan(B/2) = sec B / (sec B csc B + csc B)
Hello Johnny Walker BlackHere's the method for each one:
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.
Grandad