tan2x = 2/cotx-tanx tan2x = sin2x/cos2x
sin2x/cos2x =2/cotx - tanx sin2x = 2sinxcosx ,
cos2x = cos^2x - sin^2x
2sinxcosx
--------------------- = 2/cotx - tanx
cos^2x - sin^2x
2sinxcosx/sinxcosx
---------------------------------- = 2/cotx - tanx
(cos^2x - sin^2x)/sinxcosx
2
--------------------------------------------------- = 2/cotx - tanx
cos^2x/sinxcosx - sin^2x/sinxcosx
2
-------------------------------------------- = 2/cotx - tanx
cosx/sinx - sinx/cosx
2
----------------------------------- =2/cotx - tanx
cotx - sinx
2/( cotx - tanx) = 2(/cotx - tanx)