Let \( a, b, c, d \in R \). Then the cubic equation of the type \( a x^{3}+b x^{2}+c x+d=0 \) has either one root real or all three roots are real. But in case of trigonometric equations of the type \( a \sin ^{3} x+b \sin ^{2} x+c \sin x+d \)
\( \mathrm{P} \) \( =0 \) can possess several solutions depending upon the domain of \( \mathrm{x} \). To solve an equation of the type \( a \cos \theta+b \sin \theta=c \). The equation can be written as W \( \cos (\theta-\alpha)=c / \sqrt{\left(a^{2}+b^{2}\right)} \).
The solution is \( \theta=2 n \pi+\alpha \pm \beta \), where \( \tan \alpha=b / a, \cos \beta=c / \sqrt{\left(a^{2}+b^{2}\right)} \).
On the domain \( [-\pi, \pi] \) the equation \( 4 \sin ^{3} x+2 \sin ^{2} x-2 \sin x-1=0 \) possess
(A) only one real root
(B) three real roots
(C) four real roots
(D) six real roots
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