Question #36d3b

1 Answer
Apr 6, 2017

Please see below.

Explanation:

As typed, the question asks for #lim_(xrarr1)(x-1)^2 cos(1/x-1)#.

Interpretation 1
If you really want #lim_(xrarr1)(x-1)^2 cos(1/x-1)#, use substitution to get

#(1-1)^2 cos(1/1-1) = 0cos(0) = 0*1 = 0#

Interpretation 2

For #lim_(xrarr1) (x-1)^2 cos(1/(x-1))# argue something like this:

We know from our study of trigonometry, that

#-1 <= cos(1/(x-1)) <= 1# for all #x != 1#.

Since #(x-1)^2# is positive for all #x != 1#, we can multiply the inequality without changing the direction of the inequality.

#-(x-1)^2 <= (x-1)^2 cos(1/(x-1)) <= (x-1)^2# for #x != 1#

Note that

#lim_(xrarr1)(-(x-1)^2) = 0# and #lim_(xrarr1)(x-1)^2 = 0#.

Therefore, by the squeeze theorem,

#lim_(xrarr1) (x-1)^2 cos(1/(x-1))#