2cosa=x+1/x then cos2a=?
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Answer:
Step-by-step explanation:
L.H.S.= cos 2a
= 2 cos ^2 − 1
= 2 [1/2(x+1/x)]^2
= 1/2 (x^2 + 1/x^2 + 2.x.1/x)-1
= 1/2 (x^2 + 1/x^2)+1/2.2-1
=1/2 (x^2 + 1/x^2)
= R.H.S.
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