A:酒精(C2H5OH)属于有机化合物
B:重铬酸钾(K2Cr2O7)中铬元素的化合价为+7
C:C2H5OH的相对分子质量为46g
D:C2H5OH中C、H、O元素质量比为2:6:1
We ____ ____ ____ Kang kang's birthday party. All of us had a good time.
2的相反数是 ( )
如图,已知四边形ABCD内接于圆,对角线AC与BD相交于点E,F在AC上,AB=AD,∠BFC=∠BAD=2∠DFC.
(1)若∠DFC=40°,求∠CBF的度数;
(2)求证:CD⊥DF.
已知等差数列{an}的前n项和为Sn,且满足S33-S22=1,则数列{an}的公差是( )