When $0 \leq x < 2 \pi$, what is the sum of all solutions to the equation $$\cos ^ { 2 } x = \sin ^ { 2 } x - \sin x$$ ? [3 points]\\ (1) $2 \pi$\\ (2) $\frac { 5 } { 2 } \pi$\\ (3) $3 \pi$\\ (4) $\frac { 7 } { 2 } \pi$\\ (5) $4 \pi$