By factorising, or otherwise, solve the following equations for $0\le \theta \le 360$:

1. $${\tan }^2(\theta )+3\tan (\theta )-10=0$$
2. $$9{\cos }^2\left(\theta \right)-6\cos \left(\theta \right)+1=0$$
3. $$4{\sin }^2(\theta )-9\sin (\theta )+2=0$$

For (a), let $t=\tan (\theta ).$ Can you solve

?

For (b), let $c=\cos (\theta )$ and consider

Note that $-1\le \sin (\theta )\le 1$ so $\sin (\theta )=2$ does not lead to any solutions.