If \(y=\sin ^{98}(x) \cdot \cos ^{39}(x)\), then find \(\frac{d y}{d x}\)

If \(y=\sin ^{98}(x) \cdot \cos ^{39}(x)\), then find \(\frac{d y}{d x}\)
  1. \(\left(98 \cos ^{99} x \cdot \sin ^{38} x\right)+\left(39 \sin ^{40} x \cdot \cos ^{97} x\right)\)
  2. \(\left(99 \cos ^{98} x \cdot \sin ^{39} x\right)-\left(40 \sin ^{39} x \cdot \cos ^{98} x\right)\)
  3. \(\left(98 \cos ^{99} x \cdot \sin ^{38} x\right)-\left(39 \sin ^{40} x \cdot \cos ^{97} x\right)\)
  4. \(\left.99 \cos ^{98} x \cdot \sin ^{39} x\right)+\left(39 \sin ^{40} x \cdot \cos ^{97} x\right)\)

Solution

\(y=\sin ^{98} x \cdot \cos ^{39} x\) \(\begin{aligned} & \frac{d y}{d x}=\sin ^{98} x \cdot 39 \cos ^{38} x(-\sin x) \\ & +\cos ^{39 x} \cdot 98 \sin ^{97} x(\cos x) \\ & =98 \sin ^{97} x \cdot \cos ^{40} x-39 \sin ^{99} x \cdot \cos ^{38} x \\ & =98 \cos ^{99} x \cdot \sin ^{38} x-39 \sin ^{40} x \cdot \cos ^{97} x \\ \end{aligned}\)

Asked in: AP EAMCET 2020 (17 Sep Shift 1)

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