Question

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Answer 1

Could of sworn I answered this like 15 minutes ago, use:

Answer 2

you didnt finish answering the question

Answer 3

Lol. That's b/c you asked me to answer it for you :P
I wanted you to finish it. i provided a lot of steps.
once again, here:\[[\cos(x)\cos(y) - \sin(x)\sin(y)]-[\cos(x)(\cos(y)+\sin(x)\sin(y)] = 2\sin(x)\sin(y)\]

NOTE: distribute the negative sign across! You should be familiar with this from algebra.

Answer 4

do you keep cosx and cosy as well as sinx siny together when you distribute the negative or do you break them apart?

Answer 5

You keep them together. It's the same thing as saying -(xy-y). You don't separate them. You simply have: -xy+y. But after you distribute you will have one big function which you can combine like terms. You should kknow this from algebra.
For example, if I have:
a+2a + b - b

it's the same as 3a +0 = 3a

Answer 6

okay i understand now but i came up with - 2 sinx siny

Answer 7

I think I switched the formulas. i think the first one should of been + and the second one should of been -.

My bad. What proofs do is basically you manipulating things. So that;s all you have to do. But you get the method.

Answer 8

Thank You!