将直角坐标P(-1,)化为极坐标(ρ＞0,0≤θ＜2π)为_________.
If weather ________, we’ll go cutting. A. allows B. permits C. lets D. promises
She devoted herself_______ to her research and it earned her a good reputation in her field. A．strongly B．extremely C．entirely D．freely
如图,平面α⊥平面β,A∈α,B∈β,AB与两平面α、β所成的角分别为和.过A、B分别作两平面交线的垂线,垂足为A′、B′,则AB∶A′B′等于( )A.2∶1
Helen devoted herself ________to her research and became a top scientist in the field of applied physics． A．seriously B．extremely C．entirely
一平行板电容器C，极板是水平放置的，它和三个可变电阻及电源连接成如图所示的电路．今有一质量为m的带电油滴悬浮在两极板之间静止不动，要使油
有H、S、O、Na四种元素，按下列要求写出由它们组成物质的化学式。 （1）组成的单质的化学式（四种）
“志士仁人，无求生以害仁，有杀身以成仁。”这段论述当出自 ( ) A.儒家 B.道家 C.法家
