Trig Identities: cos^2(2x) + sin^2(2x), os^2(x)-1/sin(x),
Too bad your notation is not clear enough. If you mean for the entire expression to be in the numerator, you will need to write it like this: [cos^2(x)-1]/sin(x) = [1-sin^2(x)-1]/sin(x) = -sin^2(x)/sin(x) = -sin(x) And, really, what do you have against th...