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posted by  laughsalot on 9/28/2008 2:38:49 PM  |  status: Live  

verifying identies please help

Course Textbook Chapter Problem
Trigonometry College Trigonometry 6th edition, Aufmann, Barker, Nation 3 N/A
Question Details:
 
 
1.   tan 1/2 x = cscx - cotx
 
 
2.   1+ sin 2x  =  cos 2x
       cosx + sinx    cosx-sin x
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Sage
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posted by Maurizio on 9/28/2008 2:54:23 PM  |  status: Live
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Response Details:
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cos4x+1-(1-cos2x)2=2cos2x   cos4x+1-(1+cos4x-2cos2x) = 2cos2x .............
    
Oracle
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posted by Grace on 9/28/2008 2:56:02 PM  |  status: Live
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laughsalot's comment:
"Thank you ...you rock"
Response Details:
1. (cos2x)2 + 1 - (sin2x)2 = 2cos2x
identity: cos2x + sin2x = 1 so sin2x = 1-cos2x
(cos2x)2 + 1 - (1-cos2x)2 = 2cos2x
(cos2x)2 + 1 - [1-2cos2x + cos4x] = 2cos2x
cos4x + 1 - 1+2cos2x - cos4x = 2cos2x
Cancel: 2cos2x = 2cos2x


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