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Find Dy Dx ; If X = Sin3θ , Y = Cos3θ - Mathematics and Statistics

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Question

Find `"dy"/"dx"` ; if x = sin3θ , y = cos3θ

Sum

Solution

x = sin3 θ 

differentlating w.r.t. θ

`"dy"/("d" theta) = 3 "sin"^2 theta . "cos" theta`

Y = cos3θ

Differentiating w.r.t. θ

`"dy"/("d" theta) = 3"cos"^2 theta (-"sin" theta)`

= -3 cos2 θ . sin θ

`"dy"/"dx" = ("dy"/("d"theta))/("dx"/("d" theta)) = (-3"cos"^2  theta . "sin"  theta)/(3"sin"^2 theta . "cos"  theta) = ("- cos"  theta)/("sin"  theta) = - "cot"  theta`

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2017-2018 (July) Set 1

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