integration what am i doing wrong?

integrate the equation below:

cos²3x dx


i ended up getting.....

(1/2)x + (1/12)sin(6x) + C

the back of my book has a different awnser for this? i have no idea and i feel like this should be correct...

your answer is actually correct. What answer does your book give?

Quote:

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Originally Posted by maybnxtseasn

integrate the equation below:

cos²3x dx


i ended up getting.....

(1/2)x + (1/12)sin(6x) + C

the back of my book has a different awnser for this? i have no idea and i feel like this should be correct...

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The correct answer can be written in many different but equivalent forms. Your answer is one such form. No doubt your book's answer is another. You should apply basic trig identities to see if this is the case.