Question

Use the sum-to-product formula to find the exact value:
If \cos 255^\circ - \cos 195^\circ = \frac{\sqrt{A}}{2}

Answer 1

\[\cos 255^\circ - \cos 195^\circ = \frac{\sqrt{A}}{2}\]

Answer 2

The exact value of what?

Answer 3

of A

Answer 4

cos A - cos B= -2 sin(A+B)/2 * sin (A-B)/2

Answer 5

Can you find it now?

Answer 6

im working on it now

Answer 7

the thing is should I make A the subject in that equation and solve it?

Answer 8

Did you find cos 255- cos 195 already?

Answer 9

-2sin225*sin15

Answer 10

=.366

Answer 11

what do i do next? I tried solving -2sin225*sin15 and equating it to \[\sqrt{A}/2\] and solving for A but it was wrong