Find , when:

Formulae :

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Given,

Put x = tan a

Therefore, …………… eq (1)

y = sin (cos 2a) ………….

Differentiating above equation w.r.t. a ,

………….

………….

………….

But, x = tan a

…………………….. eq (2)

Now,

………… By chain rule

…………….. from eq (1) & eq (2)

…..…….

…..…….