Mathematics

Mathematics

Problem

For a smooth function y=f(x)y=f(x) on [a,b][a,b], which of the following definite integrals represents the exact length of the graph of ff between x=ax=a and x=bx=b? a) ∫ab∣f′(x)∣ dx\displaystyle \int_{a}^{b} |f'(x)|\,dx b) ∫ab(1+[f′(x)]2) dx\displaystyle \int_{a}^{b} \bigl(1+[f'(x)]^{2}\bigr)\,dx c) ∫ab1+[f′(x)]2 dx\displaystyle \int_{a}^{b} \sqrt{1+[f'(x)]^{2}}\,dx d) ∫ab1+[f(x)]2 dx\displaystyle \int_{a}^{b} \sqrt{1+[f(x)]^{2}}\,dx

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