Question

Can someone please tell me what they get for this?!
f '(x) =-9 (cos(x)+x cos(x)+sin(x)-x sin(x))
solve for f '(-pi/4)

Answer 1

-9 (cos(x)+x cos(x)+sin(x)-x sin(x))
substitute x = -pi/4

Answer 2

-9 (cos(-pi/4)+x cos(-pi/4)+sin(-pi/4)-x sin(-pi/4))

Answer 3

No the actual final number?

Answer 4

same value for sin(pi/4)
you need to look at the even and odd identities to see if you keep the negavtive signs.