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## Homework Statement

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

## Homework Equations

all trig identities

## 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!