Math CentralQuandaries & Queries


Question from Richter, a student:

what is the value of lim [cos (π/x)]/(x-2)?

Hi Richter,

Since cos (π/2) = 0 you have a limit where the numerator and denominator both approach zero as x approaches 2 and hence you can use l'Hopital's Rule.

d/dx(cos (π/x)) = - [sin(π/x)][- π/(x2)] and

d/dx(x - 2) = 1

Can you see how to complete the problem now?


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