How many real solutions are there to the equation $$2 \cos ^ { 4 } \theta - 5 \cos ^ { 2 } \theta + 3 = 0$$ in the interval $0 \leq \theta \leq 2 \pi$ ?
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How many real solutions are there to the equation
$$2 \cos ^ { 4 } \theta - 5 \cos ^ { 2 } \theta + 3 = 0$$
in the interval $0 \leq \theta \leq 2 \pi$ ?