Question

PLEASE HELP! Express 1 - 2sin^2 38 degrees as a function of twice the given angle.
a. cos 76 degrees
b. sin 76 degrees
c. -sin 76 degrees
d. -cos 76 degrees

Answer 1

do you know the expansions for cos(2x) and sin(2x)?

Answer 2

No I do not

Answer 3

well you need to learn those before you can answer this question.

Answer 4

sin(2x) = 2sin(x)cos(x)

cos(2x) = cos2(x) – sin2(x) = 1 – 2sin2(x) = 2cos2(x) – 1

Answer 5

that is correct - now which one of those looks like the equation in your question?

Answer 6

cos(2x)?

Answer 7

correct - hopefully you know what to do know?

Answer 8

*now

Answer 9

Yes, I think so... Thanks

Answer 10

yw :)

Answer 11

The answer is A. correct?

Answer 12

yes :)

Answer 13

:D