If co s^4 - ^4 = 2/3, then the value of 1 - 2 ^2 is?

Answer: Option C

$$\begin{array}{rl}& \text{co}{\text{s}}^4\theta -{\sin }^4\theta =\frac{2}{3}\\ & \Rightarrow \left(\text{co}{\text{s}}^2\theta -{\sin }^2\theta \right)\left(\text{co}{\text{s}}^2\theta +{\sin }^2\theta \right)=\frac{2}{3}\\ & \Rightarrow \text{co}{\text{s}}^2\theta -{\sin }^2\theta =\frac{2}{3}\\ & \Rightarrow 1-{\sin }^2\theta -{\sin }^2\theta =\frac{2}{3}\\ & \Rightarrow 1-2{\sin }^2\theta =\frac{2}{3}\end{array}$$