Use l'hopsital RUle to solve for
lim x--Pi / 4 5(1-tanx)secx.

I solve for the equation (by plugging in pi/4) and I don't get zero, however, my answer is still wrong, should I still use the hospital rule?

Question

Use l'hopsital RUle to solve for
 lim x-->Pi / 4     5(1-tanx)secx.

I solve for the equation (by plugging in pi/4) and I don't get zero, however, my answer is still wrong, should I still use the hospital rule?

tkhunny · Answer

$\tan\left(\dfrac{\pi}{4}\right) = 1$

$\sec\left(\dfrac{\pi}{4}\right) = \sqrt{2}$

1) Never "plug in".  Sometimes substitution is approprate.
2) This is not an indeterminate form.  Please don't use l'Hopital's Rule.
3) Please supply the ENTIRE problem statement.

anonymous · Answer

That is the entire problem. and I should've calculated in radian... right?

tkhunny · Answer

You can calculate in Light Years if you like.  It's NOT an indeterminate form.

tkhunny · Answer

That doesn't mean we can't find the limit.  We just can't use (or don't need) l'Hopital's Rule.