如图,以O为圆心的两个同心圆中,大圆的弦AB与小圆相切于点C,若大圆半径为10cm,小圆半径为6cm,则弦AB的长为 cm.
-0.4×0.2=_______;
(-5)×(3)=_______;
(-3)×(-0.3)=_______;
确定下列各个积的符号,填在空格内: (1)(-7.4)×(-3.2)_______; (2)(-2)×(-2)×2×(-2)________; (3)(-)×(-)×(-)×(-)
计算填空,并说明计算依据: (1)(-3)×5=______(); (2)(-2)×(-6)=_______(); (3)0×(-4)=________();