放样基准选择有三种类型,()是其中之一。
A.以两条中心线为基准
B.随便选择
C.不用基准
参考答案:A
It ____ Jack twenty minutes ____ the math problem yesterday.
A.took; to work out
B.takes; worked out
C.has taken; work out
D.is taking; working out
下列各式中不成立的是( )
A.sin260°+sin230°=1 B.cot45°<cot35°C.tan45°>sin45° D.sin30°+cos30°=1