如图,AB切⊙O于点B,OA=2,∠OAB=30°,弦BC∥OA,劣弧的弧长为 .(结果保留π)
若x2=25,则x=_____; 若,则x=_____;若,则x=_____; 若x3=﹣216,则x=_____;若=3,则x=_____;若,则x=_____.
填空: (1)的立方根为_____(2)﹣0.008的立方根为_____(3)512的立方根为_____(4)36的立方根为_____.
﹣64的立方根是_____,﹣是_____的立方根.
﹣1的立方根是_____,0的立方根是_____,的立方根是_____.
若=4,则=_____.