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If y = log [cos(x5)] then find dydx

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Question

If y = log [cos(x5)] then find `("d"y)/("d"x)`

Sum
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Solution

y = log [cos(x5)]

Differentiating w.r.t. x, we get

`("d"y)/("d"x) = "d"/("d"x)[log{cos(x^5)}]`

= `1/(cos(x^5))*"d"/("d"x)[cos(x^5)]`

= `1/(cos(x^5))*[-sin(x^5)]*"d"/("d"x)(x^5)`

= `(-sin(x^5))/(cos(x^5))*5x^4`

= – 5x4 tan(x5)

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Chapter 2.1: Differentiation - Short Answers I

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