I would use:

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- November 13th 2012, 06:49 PM #1
## Does this Look right?

Suppose and is

**negative**. Here are some small variations on the previous problems:

Which one of the two addition formals would put me on the right way?

sin(u-pi)=sin(u)cos(pi)-cos(u)sin(pi)

or

sin(-(12/13)-pi)= sin-(12/13)cos(pi)-cos-(12/13)sin(pi)?

- November 13th 2012, 06:58 PM #2

- November 13th 2012, 07:35 PM #3

- November 13th 2012, 07:37 PM #4

- November 13th 2012, 08:17 PM #5

- November 13th 2012, 08:39 PM #6

- November 13th 2012, 08:42 PM #7

- November 13th 2012, 09:15 PM #8