Question

f '(x) =-9 (cos(x)+x cos(x)+sin(x)-x sin(x))
solve for f '(-pi/4)

Answer 1

you can plug this into the caluculator?

Answer 2

This is just a matter of plugging in, remember your unit circle:
\[\cos \frac{-\pi }4=\frac{\sqrt{2}}{2}\]
\[\sin \frac{-\pi }4=\frac{\sqrt{2}}2\]
just plug and for your cos/sin and go go combines/simplifies.