If $\displaystyle f'(x)= cos(x^2-1) and f(-1)=1.5, then f(5)= ? $

so far i have:

$\displaystyle \int_{-1}^5 cos(x^2-a) dx= f(5)-f(-1)$

i let $\displaystyle u=x^2-1 $

$\displaystyle du=2x $

Mr F says: du = 2x dx =>dx = du/(2x). This will lead nowhere for you because the x will cause trouble. The integral cannot in fact be found using a finite number of elementary functions.
change the limits from x=5 to u=24, x=-1 to u=0 and have

$\displaystyle 1/2 \int_0^{24} cos(u) du + f(-1) $

Mr F says: Wrong. What happened to the 1/x part of du ....?
which gives me -1.788 but that isn't any of the answers provided!