# Math Help - lets see if you can get this beast

1. why does y= x-1 though?

2. Originally Posted by winterwyrm
why does y= x-1 though?
There are two reasons, not entirely independent.
1) He wanted the limit to go to 0 so he could use his approximation for the cotangent.

2) It works. That's pretty much the final reason for using any method.

-Dan

3. Originally Posted by winterwyrm
why does y= x-1 though?
As topsquark says, basically I want to use small angle approximations for the
trig function, and this substitution makes it easier to see what I am doing.

Also If I wanted to do a power series expansion, then if the limiting variable
is going to zero and I have expanded about 0, then I can discard the higher
order terms (but this is essentially the same reason as above).

Unless the limit is obvious it is the first move I normally make.

RonL

Page 2 of 2 First 12