Q) 1- tan 2 A / 1 + tan 2 A = 2cos 2 A - 1 .. PROVE THAT
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1-(sin^2 A/ cos^2 A)/1+(sin^2 A/cos^2 A)
= (cos^2 A - sin^2 A/cos^2)/ (cos^2 A + sin^2 A/ cos^2 A)
= cos^2 A-sin^2 A
= cos^2 A - (1-cos^2 A)
= 2 cos ^2 A - 1
sin^2 A + cos^2 A = 1
> cos^2 A = 1- sin^2 A
= (cos^2 A - sin^2 A/cos^2)/ (cos^2 A + sin^2 A/ cos^2 A)
= cos^2 A-sin^2 A
= cos^2 A - (1-cos^2 A)
= 2 cos ^2 A - 1
sin^2 A + cos^2 A = 1
> cos^2 A = 1- sin^2 A
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