SOLUTION: if y =sqrt(cos x sqrt cos x sqrt (cos(x)* ....to ∞))), find dy/dx

Question 1158465: if y =sqrt(cos x sqrt cos x sqrt (cos(x)* ....to ∞))),
find dy/dx

Answer by ikleyn(52786) (Show Source): You can put this solution on YOUR website!
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if y = sqrt(cos(x) * sqrt (cos(x) * sqrt (cos(x)* ....to ∞))).

find dy/dx
~~~~~~~~~~~~~~~~~~

Square both sides.  You will get   

     = cos(x)*y.


Cancel "y" in both sides. You will get

    y = cos(x).


Take the derivative

    y' = -sin(x).


It is your answer.

Solved.

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