∫ π2 0sinxdx=(-cosx)|π20=0-(-1)=1,
故选D.
You_____ all those calculations! We have a computer to do that sort of thing.
A.needn’t have done
B.must not have done
C.shouldn’t have done
D.can not have done
非水滴定法测定维生素B1原料药的含量,应选
A.淀粉指示剂B.喹哪啶红-亚甲蓝混合指示剂C.二苯胺指示剂D.邻二氮菲指示剂E.酚酞指示剂