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treez 
Posted: August 25, 2012 08:38 am

Unregistered 
Hello,
How do you derive the equation at the bottom left of page three of this..... http://www.fairchildsemi.com/an/AN/AN4151.pdf ...that is, how does the expression containg alll the w's come out from the expression containg a sine in the numerator and denominator?.. ..is there some standard substitution you can do for the sine expressions? 

Sch3mat1c 
Posted: August 25, 2012 05:25 pm

Forum Addict ++ Group: Moderators Posts: 19,532 Member No.: 73 Joined: July 24, 2002 
Substitution, cancellation, substitution again.
 Answering questions is a tricky subject to practice. Not due to the difficulty of formulating or locating answers, but due to the human inability of asking the right questions; a skill that, were one to possess, would put them in the "answering" category.

Village Idiot 
Posted: August 25, 2012 07:28 pm

Forum Addict ++ Group: Trusted Members Posts: 1,581 Member No.: 11,398 Joined: October 08, 2007 
The applicable substitution appears to be:
sin(x)/sin(x)=1 
treez 
Posted: August 26, 2012 12:52 pm

Unregistered 
Thanks, i cant find them in maths book, do you just call them "sine substitutions"


Village Idiot 
Posted: August 26, 2012 08:35 pm

Forum Addict ++ Group: Trusted Members Posts: 1,581 Member No.: 11,398 Joined: October 08, 2007 
Try looking for "trigonometric identities"
Lot's of info here: http://en.wikipedia.org/wiki/Trigonometric_identities Actually, it's a bit of information overload. Generally, useful in electronics are the sumtoproduct and producttosum transformations, which you can find on that page. What I mentioned in my previous post doesn't even qualify as a trigonometric substitution. It was simply two identical terms in the numerator and denominator which automatically cancel out. It had nothing to do with the fact that it was a sine function. 
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