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cos2x = 2-sec^2x/sec^2x

0 votes
identity problem.
asked Mar 10, 2014 in TRIGONOMETRY by rockstar Apprentice

1 Answer

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[We know that Cos2x = Cos^2x - Sin^2x

Cos2x  = Cos^2x - (1-Cos^2x)

Cos2x  = 2Cos^2x - 1]

Right hand side identity

= (2-Sec^2x)/Sec^2x

= 2/Sec^2x - Sec^2x/Sec^2x

= 2/Sec^2x - 1

= 2Cos^2x -1

= Cos2x

= Left hand side identity.

answered Mar 10, 2014 by david Expert

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