How is cos x -x(sin x) the same as cos x-x?

Question

anonymous · Answer

who said it was?

anonymous · Answer

Im looking to the derivative of (x) (cos x)
Using the Product Rule I get:
(1) (cos x) + (x)(-sin x)

Book says answer is cos x -x

anonymous · Answer

attachment

anonymous · Answer

the textbook cut off the sinx. you answer is right.

you'll see that textbooks are filled with mistakes :P

anonymous · Answer

certainty: 100%

you can even try it with your calculator (make sure it's in radians)

anonymous · Answer

thanks @Euler271! Glad i'm not crazy, I was here trying to find the answer!

anonymous · Answer

I tried it with the calculator the first time, but i didnt realize it was in degrees, not radians so i was even more confused lol

anonymous · Answer

lol :P

ya. textbooks have made me doubt my sanity too. i've wasted hours on problems before only to find out i was right.

glad i could help ^_^