Not -3 sin (6x) ?but the answer says it's -3cos(6x).
They got your answer, and then applied a double-angle identity to get their form, -3sin(6x). Both are correct answers.It should be [imath]-3 \sin(6x)[/imath]
Oh, I meant the answer should not be [imath]-3\cos(6x)[/imath].They got your answer, and then applied a double-angle identity to get their form, -3sin(6x). Both are correct answers.
I was confusing you with the OP. I'd like to know why they said the book gave a wrong answer. My "your" referred to the OP:Oh, I meant the answer should not be [imath]-3\cos(6x)[/imath].
I have to differentiate (cos (3x))^2 which I did and got -6cos(3x)sin(3x), but the answer says it's -3cos(6x).....please help! Thanks