which cofunction identities would u use

cos (x+pi/2)=-sinx or sin (x+pi/2)=cosx? how did u determine which one to use?

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- Apr 6th 2009, 11:27 AMjepal[SOLVED] Given sin (pi/6)=1/2 use an equivalent trig expression to show cos 2pi/3=-1/
which cofunction identities would u use

cos (x+pi/2)=-sinx or sin (x+pi/2)=cosx? how did u determine which one to use? - Apr 6th 2009, 11:58 AMstapel
- Apr 6th 2009, 12:00 PMjepal
- Apr 6th 2009, 12:29 PMicemanfan
- Apr 6th 2009, 12:29 PMjepalsolved
ignore this question....i got the answer. :D