Try it on paper first. A hint, the key idea and the worked solution are here when you need them.
A numerical analyst studies the error of a three-term approximation of the exponential. The error ratio is , for . The top and the bottom both vanish at . Apply L'Hôpital's rule repeatedly, checking the form each time, to find the limit of as tends to , to four decimal places. Also say how many times the rule is used.
Series for small : , . L'Hôpital's rule: for or , if the second limit exists.
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Given. , a form at .
Plan. Differentiate the top and the bottom, and stop when the form is gone.
Step 1. First use. The top gives and the bottom gives . At both vanish, so the form is still .
Step 2. Second use. The top gives and the bottom gives . Both vanish again.
Step 3. Third use. The top gives and the bottom gives . This is not indeterminate: .
Step 4. The answer. The limit is , and the rule was used times.
Check. The series gives the same: the top is
Answer: the limit is and the rule is used times.
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