Trig Fuctions help!!!! plz hi everyone, my Trig text book, is really vague and I'm not sure where i could find better information. Basically, I'm not sure how to add, subtract, multiply, or divide trig functions. My text siad that to make a sinusoid the periods must be the same, and that the period is always 2 pi...!?! My book didn't even attempt to sauggest why--I'd really like to know what THE RULES FOR COMBINING AND TRANSFORMING TRIG FUNCTIONS ARE. Thankyou to anyone who can send me in the right direction.