1.

$$\frac{{\sin \theta+ \cos \theta }}{{{\text{sin}}\theta- \cos \theta }} = 3,$$then the value of $${\sin ^4}\theta- {\text{co}}{{\text{s}}^4}\theta $$is?

A. $\frac{1}{5}$$
B. $\frac{3}{5}$$
C. $\frac{2}{5}$$
D. $\frac{4}{5}$$
Answer» C. $\frac{2}{5}$$


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