dy/dx= 128[sin^3x(4cos^3x(-sinx))+cos^4x(3sin^2x(cosx))]
=128[-4sin^4xcos^3x + 3cos^5xsin^2x]
d^2y/dx^2 = 128{[cos^3x(-16sin^3x(cosx)) +
(sin^4x)(-12cos^2x(-sinx))] +
[sin^2x(15cos^4x(-sinx))+cos^5x(6sinx(-cosx))]}
Simplify this and u'll get the required answer.
~Cheerio!!!
Moderation Team
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