Derivative of y = (1/x) + sqrt(cos x)

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SUMMARY

The derivative of the function y = (1/x) + sqrt(cos x) was evaluated at the point (pi/2, 2/pi). The power rule was applied to (1/x) and the chain rule to sqrt(cos x). The derivative becomes undefined at x = pi/2 due to the square root of cos(x) being negative in certain intervals, which restricts the domain of the function. The discussion emphasizes the importance of analyzing the domain of the derivative to avoid confusion regarding undefined values.

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Homework Statement


Evaluate the derivative of the function y = (1/x) + sqrt(cos x) at the given point, (pi/2, 2/pi)

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The Attempt at a Solution


I used power rule on (1/x) and chain rule on sqrt(cos x) but when I was simplifying, there is a sqrt(cos x) in one of the denominators, which then becomes undefined when I plug in pi/2, so I'm confused what I did wrong, I'm pretty sure I used the correct rules and I'm pretty sure I simplified correctly, so why is it coming out undefined
 
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Take a look at the domain of the derivative you calculated.
 
Lord Anoobis said:
Take a look at the domain of the derivative you calculated.
What's more, Michelle, take a look at the domain of ##y = \frac 1 x + \sqrt{\cos x}##. Consider the fact that there are intervals where cos(x) is negative, so its square root isn't real on those intervals.
 

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