Show that, for small values of $\theta$ measured in radians,

$3\cos 2\theta +\sin 4\theta -2\tan 3\theta \approx A+B\theta +C{\theta }^2$

where $A$, $B$ and $C$ are constants to be found.

Use your answer to part (a) to find an approximation for

$3\cos 0.12+\sin 0.24-2\tan 0.18$

Give your answer to three decimal places.