prove that
sin(n+1)A sin(n-1)A + cos(n-1)Acos(n-1)A = cos2A?
AbhishGS:
check whether question is correct. is there is sign mistake
-/+
no there is no sign mistake
in my book
is it sin(n+1)A.sin(n-1)A+cos(n+1)A.cos(n-1)A=cos2A ?
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just to know every formulae
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thank you for the answer
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