Solution

ID: past-exam-of-the-mathematics-course-of-the-year-1-of-the-natural-sciences-course-of-the-university-of-cambridge/2020/paper-1/15/b/solution

For , the first two derivatives are and . Since ,
The first three terms of the Taylor expansion, with , therefore give
For a check on accuracy, is positive and decreasing on . The Taylor remainder is consequently positive and less than . The approximation is a slight underestimate.

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