Recent content by mathnewb

i mean ((x+y)/2)

Homework Statement cosx - cosy=-2 sin(x + y/2) sin(x - y/2) Homework Equations dont know what identities to use The Attempt at a Solution ok so when i figure it out, the RHS always comes out to either... (cos x sin y - sin x cos y)/2 or just cos x sin y - sin x cos y...

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/tanxHomework Equations all trig identitiesThe Attempt at a Solution 1) i understand that i should show what i have attempted but there is way too...