—The player looks better because the coach has got her every day.
— Yes, practice makes perfect.
A:a little bit; practice
B:a bit; practicing
C:a bit of; practice
D:a little; to pratice
已知三棱柱ABC-A1B1C1的侧棱与底面边长都相等,A1在底面ABC上的射影为BC的中点D,则异面直线AD与CC1所成的角的余弦值为( )
给出下列四个命题:①命题“若α=π4,则tanα=1”的逆否命题为假命题;②命题p:任意x∈R,都有sinx≤1,则“非p”:存在x0∈R,使sinx0>1;③“φ=π2+kπk∈Z”是“函数y=sin2x+φ为偶函数”的充要条件;④命题p:存在x0∈R,使sinx0+cosx0=32 ;命题q:△ABC中,A>B⇔sinA>sinB,那么命题“‘非p’且q”为真命题.其中正确的个数是( )
请你在空白处填写适当的内容:
已知在映射f:A→B中,A=B=x,y|x,y∈R,且f:x,y→x-y,x+y,则与A中的元素(-1,2)对应的B中的元素为( )