Solution

ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2011/ia/paper-1/11e/ii/solution

Away from zero, the product and composition of the displayed smooth functions are continuous and differentiable. At zero,
so remains continuous. Hence the continuity set is .
The difference quotient at zero is . For it equals one, and for it equals minus one. Both sequences tend to zero, so no derivative exists there. For , the product rule and chain rule give
Thus the differentiability set is .

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