how is 2cos^2x-1=cos2x?

Dear student,

\cos (2 x) = \cos (x + x) use \cos (A + B) = cosAcosB - sinAcosB \cos (2 x) = \cos (x + x) = cosxcosx - sinxcosx \cos (2 x) = \cos (x + x) = \cos^{2} x - \sin^{2} x use \sin^{2} x = 1 - \cos^{2} x \cos (2 x) = \cos (x + x) = \cos^{2} x - 1 + \cos^{2} x \cos (2 x) = 2 \cos^{2} x - 1

Hope this information will clear your doubts. If you have any more doubts just ask here on the forum and our experts will try to help out as soon as possible.

Regards

View Full Answer