说明下列方程组在空间直角坐标系中表示怎样的曲线：[tex=8.214x3.357]7EJHVCtO2IWq3KpdB+jQsv6FwiTm8kMJkqqPTKC4ZLC1wTkxS+EPmx95ijZfa7Uufjxrmdczba8ntXVnzPdRstDt6+kyeqgQ2tNSZTZpwIGgXCUx96XRAmQFiiQPB9qE[/tex]

试求曲线[tex=8.214x3.357]Vf1BpGuhboJ+vk8Sjaeoqyt8n0eyivLKVNgasuH4VSwSwiXYcPes/hOoLk7mRgcXKVXBgnMhYrluKohPgijaUsiIPvsUKi0nAAwEfS4SsM6gEnWJQ8jDBr/gw7HnWpUe[/tex]绕 [tex=0.5x0.786]C7x+w8+jOPZzxFrGGne6Dw==[/tex]轴旋转的方程.

[tex=2.929x1.286]yv1zrDENpB3HQfTPl0UFBw==[/tex][tex=8.214x3.357]fnpmC2J6JmQBLyo5NmGAz6ZQNnPbkndWonrvOOQELtedRed+cBDf8XklaM6BCagKf50VlzSmqGoIqP+qQjLbHzQ2zP29uUz1uvNbsFS3kvPXOMzNxu5QBcYTLmDGjRXj[/tex][tex=18.571x1.286]1N874BKm0VaQw/QokF5rV+ughRQSKHvvr+3zJQ3sg1UFiD75LbmKjmusMu7hx2F4BKKAcRz155Wz15uoNkkK7g+NAYRmVhXHffO3cAolN/0=[/tex][tex=11.5x1.286]MsH9nlGZheAZBoo1RxAJpBNHPInP77B+s6kxioHJ/pnlhY89ARHh1QmzjaXuKes/[/tex]

导出用梯形公式求解[tex=8.214x3.357]7EJHVCtO2IWq3KpdB+jQskomXAAKtxzZpzIgJE3bhk3V8PPXAhyljo1JSeyghAx9zXZ7fAbubhOPSM+0WEZK2roDUN+6J1fA2mLMTToupykozGGi+EkES9ZN6m/Mq2Pw[/tex]的计算公式[tex=5.929x2.786]LYvxw+LoUf33HxHaJ1T0gVM13/4gIHzdI29WzRIKg0JNiYcX7Murpc6L9dwUbTwf[/tex]取 [tex=2.286x2.357]rt5pf0ShA6sWsZruwvCeug==[/tex], 计算[tex=1.786x1.357]mOtnZh8tN3G4Lsi1abQegQ==[/tex]的近似值.

图示压杆体系中，弹簧支座刚度为[img=64x44]180379b3117202b.png[/img]，则该体系的临界荷载为kl的（ ）倍。[img=3924x1660]180379b32884d13.jpg[/img] A: 0.411 B: 1 C: 1.645 D: 3.357

图示压杆体系中，弹簧支座刚度为[img=64x44]1802df48734317e.png[/img]，则该体系的临界荷载为kl的（ ）倍。[img=3924x1660]1802df4888c0309.jpg[/img] A: 0.411 B: 1 C: 1.645 D: 3.357

下列变量组（）是一个闭回路。 A: {x，x，x，x，x，x} B: {x，x，x，x，x} C: {x，x，x，x，x，x} D: {x，x，x，x，x，x}

以下谓词蕴含式正确的是（）: (∀x) (A(x)→B(x))=>( ∀x)A(x)→(∀x)B(x)|(∀x) (A(x)↔B(x))=>( ∀x)A(x)↔(∀x)B(x)|(∀x)A(x)∨(∀x)B(x)=>( ∀x) (A(x)∨B(x))|(∃x) (A(x)∧B(x))=>(∃x)A(x)∧(∃x)B(x)

以下谓词蕴含式正确的是（）: (?x) (A(x)→B(x))=>( ?x)A(x)→(?x)B(x)|(?x) (A(x)?B(x))=>( ?x)A(x)?(?x)B(x)|(?x)A(x)∨(?x)B(x)=>( ?x) (A(x)∨B(x))|(?x) (A(x)∧B(x))=>(?x)A(x)∧(?x)B(x)

下列式中错误的是： A: (∀x)(A(x)Úp(x)) Û (∀x)A(x)Ú (∀x)p(x) B: ($x)A(x) Ù p Û ($x)(A(x) Ù p ) C: (∀x)(A(x)ÚB(x)) Þ (∀x)A(x)Ú( ∀x)B(x) D: ($x)(A(x)ÙB(x)) Þ ($x)A(x)Ù( $x)B(x)