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July 30th, 2018, 09:21 AM   #1
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Cosine approximation

how to arrive at (9.11) from (9.10) ? I am stucked during the steps





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July 30th, 2018, 01:42 PM   #2
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$\cos(w_{in}-w_{in})t-\cos(w_{in}+w_{in})t
=\cos^2w_{in}t+\sin^2w_{in}t-\cos^2w_{in}t+\sin^2w_{in}t=2\sin^2w_{in}t$

This may help.
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Last edited by skipjack; August 1st, 2018 at 03:08 PM.
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August 1st, 2018, 06:01 AM   #3
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but the integral of sin() gives -cos() ?

Do you have any further suggestions ?
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August 1st, 2018, 02:27 PM   #4
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The term with the integral inside the bracket must be small for the approximation to make sense. Can you estimate it?
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August 1st, 2018, 03:21 PM   #5
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Is it really an indefinite integral? If so, how come no constant of integration is given?
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August 1st, 2018, 07:34 PM   #6
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Vm is assumed to be of small magnitude. <-- How does this help in the approximation towards expression (9.11) ?

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Last edited by promach; August 1st, 2018 at 07:38 PM.
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