共50条信息
已知直线\(l_{1}\):\(A_{1}x+B_{1}y+C_{1}=0\),\(l_{2}\):\(A_{2}x+B_{2}y+C_{2}=0(A_{1},B_{1},C_{1},A_{2},B_{2},C_{2}\)为常数\()\),若直线\(l_{1}⊥l_{2}\),则\(A_{1}A_{2}+B_{1}B_{2}=0.(\) \()\)
命题:“若\({{a}^{2}}+{{b}^{2}}=0(a,b\in R)\),则\(a=b=0\)”的逆否命题是( )
下列语句中是命题的是( )
下面语句中,是命题的有________\((\)写出序号\()\),其中是真命题的有________\((\)写出序号\()\).
\(①\)有两个内角之和大于\(90^{\circ}\)的三角形是锐角三角形吗?
\(②\sin \dfrac{π}{3} > \cos \dfrac{π}{3}\);
\(③\)若\(x\)\(+\)\(y\)是有理数,则\(x\),\(y\)都是有理数;
\(④\)把函数\(y\)\(=2\)\({\,\!}^{x}\)的图象向上平移一个单位.
进入组卷