The curve [itex] y = \cos 3x + 2[/itex] intersects the line [itex]y = 2x[/itex] at point [itex]A[/itex], whose x co-ordinate is [itex]\alpha[/itex]. Show that [itex] 0.7 < \alpha < 0.8 [/itex]. So far I've got: Upon intersection [itex]2x = \cos 3x + 2 \Rightarrow \cos 3x - 2x = - 2 [/itex]. This doesn't seem to help. I know we've done this type of thing ages ago, but I've since lost my notes and my minds gone blank. Any help would be appreciated.