Evaluate the limit #lim_(x to pi) (e^sinx -1)/(x-pi)# without using L'Hôpital's rule?

Question

6023 views around the world

You can reuse this answer
Creative Commons License

Answer 1 · 2018-05-13T21:21:40

#-1#

#lim_(x to pi) ((e^sin(x)-1)/(x-pi))#

With #y = x - pi#

#= lim_(y to 0) ((e^sin(y + pi)-1)/(y))#

Aside:

#= lim_(y to 0) ((e^(-sin(y))-1)/(y))#

If we can use the definition of the exponential function, ie:

# e^z=\sum _{k=0}^{oo }z^{k}/(k!)=1+z+z^{2}/2 +z^{3}/6 +\cdots #

Then #e^(-sin(y))# can be expanded as:

#= lim_(y to 0) ((1 -sin(y) + 1/2 (-sin^2 y) + .... )-1)/(y)#

#= lim_(y to 0) ( -sin(y) + 1/2 sin^2 y + .... )/(y)#

#=- lim_(y to 0) ( sin(y) - 1/2 sin^2 y + .... )/(y) = -1#