The value of $\cos ec 45°$ is

Let $P=(\theta :\sin \theta -\cos \theta =\sqrt{2}\cos \theta \}$ and $Q=\{\theta :\sin \theta +\cos \theta =\sqrt{2}\sin \theta \}$ be two sets. Then,

If $3\sin \theta =2{\cos }^2\theta , 0^0<\theta <{90}^0$. Then the value of $({\tan }^2\theta +se{c}^2\theta -\cos e{c}^2\theta )$ is: