Please check my work. The answer of this question is 2 lpl.
I got the answer is 2p. Could you please help me find out the reason? Thank you very much.
In this case take the curvature as:
where we consider as a function of and differentiation is with respect to
This has and interchanged compared to the usual expression but the absolute value of the curvature is the same either way, and this way is easier to handle.
Here:
so:
,
and:
so at , , so:
so the radius of curvature .
RonL