prove that cos x+cos y+cos z+cos(x+y+z)=4cos{(x+y)/2}*cos{(y+z)/2}*cos{(z+x)/2}

Asked by Athira Sasidharan | 16th Sep, 2013, 05:27: PM

Expert Answer:

Answered by  | 17th Sep, 2013, 09:02: AM

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