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 October 12th, 2011, 06:03 PM #1 Newbie   Joined: Oct 2011 Posts: 21 Thanks: 0 trig- identities Hello I'm having trouble with trig identities. Here is an example problem. (Csx+cotx) (1-cosx) Haven't done these for a while. What do I do?
 October 12th, 2011, 06:42 PM #2 Senior Member     Joined: Jul 2010 From: St. Augustine, FL., U.S.A.'s oldest city Posts: 12,209 Thanks: 517 Math Focus: Calculus/ODEs Re: trig- identities We are given: $$$\csc x+\cot x$$$$1-\cos x$$$ Express the first factor in terms of sine and cosine: $$$\frac{1}{\sin x}+\frac{\cos x}{\sin x}$$$$1-\cos x$$$ $\frac{$$1+\cos x$$$$1-\cos x$$}{\sin x}$ $\frac{1-\cos^2x}{\sin x}=\frac{\sin^2 x}{\sin x}=\sin x$
 October 12th, 2011, 06:48 PM #3 Newbie   Joined: Oct 2011 Posts: 21 Thanks: 0 Re: trig- identities Thanks man! All of that makes sense except how does 1- happen in 1-cos^2x?
 October 12th, 2011, 06:57 PM #4 Senior Member     Joined: Jul 2010 From: St. Augustine, FL., U.S.A.'s oldest city Posts: 12,209 Thanks: 517 Math Focus: Calculus/ODEs Re: trig- identities It's a difference of squares: $x^2-y^2=(x+y)(x-y)$ Where in our case $x=1$ and $y=\cos x$.

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