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If ∫sin⁡4xcos⁡8x dx=atan⁡7x+btan⁡5x+C\displaystyle\int \dfrac{\sin^4 x}{\cos^8 x}\, dx = a\tan^7 x + b\tan^5 x + C, where 'C' is an arbitrary constant then

Solution

✅ Correct Option: 2

Write the integrand as tan⁡4xsec⁡4x=tan⁡4x(1+tan⁡2x)sec⁡2x\tan^4x\sec^4x=\tan^4x(1+\tan^2x)\sec^2x.

Put t=tan⁡xt=\tan x: ∫(t4+t6)dt=t77+t55\int (t^4+t^6)dt=\dfrac{t^7}{7}+\dfrac{t^5}{5}.

So a=17a=\dfrac17, b=15b=\dfrac15, giving 5b=1=7a5b=1=7a.

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