question_answer

If\[\mathbf{cos}\,\mathbf{3}x\mathbf{=4}\,\mathbf{co}{{\mathbf{s}}^{\mathbf{3}}}\mathbf{30{}^\circ }-\mathbf{3co}{{\mathbf{s}}^{\mathbf{3}}}\mathbf{0{}^\circ }\]then the  value of x is ________

A)  0                                                                    

B)  \[30{}^\circ \]         

C)  \[20{}^\circ \]                                                             

D)  \[15{}^\circ \]

E)  None of these