Question

hey guys please do it.

Answer 1

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cos θ = 1/2 ( a + 1/a)

Now,
cos 2θ = 2cos2θ -1
           = 2( 1/2 (a + 1/a))2 -1
           = 2(1/4(a2 + 1/a2 +2)) -1
           = 1/2 (a2 + 1/a2 + 2) -1
           = 1/2(a2 + 1/a2) +1 -1
           = 1/2(a2 + 1/a2 )

Hence, proved!
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Answer 2

Step-by-step explanation:

your answer is in the attachment