Question

$if \: \: cos {}^{2} x(\pi \div 6) = 2 \: find \: \: x$



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Answer 1

Answer:

We have f(x)=cos(2x+4π) 

dxdy=−2sin(2x+4π) 

Since, 83π<x<87π

⇒43π<2x<47π

⇒π<2x+4π<2π

i.e 3rd and 4th quadrant 

So, sin(2x+4π) is negative 

⇒dxdy is positive 

Hence, f(x) is increasing in the given interval