In the question, cos2x=cos^2x-sin^2x=2cos^2x-1... Why is 2cos^2x-1 is used?
K ken_165 New member Joined Jun 9, 2018 Messages 11 Jun 16, 2018 #1 In the question, cos2x=cos^2x-sin^2x=2cos^2x-1... Why is 2cos^2x-1 is used?