1. The problem statement, all variables and given/known data 1) sin(x+y)sin(x-y)=cos^2y-cos^2x 2) tan(∏⁄4+x)+tan(∏/4-x)=2sec2x 3) cosx-cosy=-2sin(x+y/2)sin(x+y/2) 4) 2cotx-2tanx=4-2sec^2x/tanx 2. Relevant equations all trig identities 3. The attempt at a solution 1) i understand that i should show what i have attempted but there is way too many lines of manipulating the equations and i don't have the time to write it down. i can say that for all of these identities i have changed them to cos and sin as these can be the easiest to solve and then used trig identities to make both sides look the same. i have nt had any luck with these and i was hoping you guys could help me thx alot!