• 2022-06-08
    (接上题)(2)如果它由入射波与反射波叠加而形成,则产生此驻波的入射波和反射波的波函数为
    A: $y_{1}=0.005cos(314t-3.14x),y_{2}=0.005cos(314t+3.14x);$
    B: $y_{1}=0.005cos(314t+3.14x),y_{2}=0.005cos(314t+3.14x);$
    C: $y_{1}=0.005cos(314t-3.14x),y_{2}=0.005cos(314t+3.14x\pm \pi);$
    D: $y_{1}=0.005cos(314t+3.14x),y_{2}=0.005cos(314t-3.14x);$
  • C

    举一反三

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    • 0

      以下集合对于所指的线性运算构成实数域上线性空间的有 ( )。 A: $R^{2}$上定义加法,数乘如下:$$(x_{1},x_{2})+(y_{1},y_{2})=(x_{1}+y_{1},0),k(x,y)=(kx,0)$$ B: $R^{2}$上定义加法,数乘如下:$$(x_{1},x_{2})+(y_{1},y_{2})=(x_{1}+y_{1},x_{2}),k(x,y)=(kx,y)$$ C: 平面上不平行于$X$ 轴的向量全体,关于向量的加法与数量乘法 D: $R^{2}$上定义加法,数乘如下:$$(x_{1},x_{2})+(y_{1},y_{2})=(x_{1}+y_{1},x_{2}+y_{2}+x_{1}y_{1})),$$$$k(x,y)=(kx,ky+\frac{k(k-1)}{2}x^{2})$$

    • 1

      曲线$\left\{ \matrix{ {x^2} + {y^2} + {z^2} = 9 \cr y = x \cr} \right.$的参数方程为( ). A: $$\left\{ \matrix{ x = \sqrt 3 \cos t \cr y = \sqrt 3 \cos t \cr z = \sqrt 3 \sin t \cr} \right.(0 \le t \le 2\pi )$$ B: $$\left\{ \matrix{ x = {3 \over {\sqrt 2 }}\cos t\cr y = {3 \over {\sqrt 2 }}\cos t \cr z = 3\sin t \cr} \right.(0 \le t \le 2\pi )$$ C: $$\left\{ \matrix{ x = \cos t\cr y = \cos t\cr z = \sin t \cr} \right.(0 \le t \le 2\pi )$$ D: $$\left\{ \matrix{ x = {{\sqrt 3 } \over 3}\cos t\cr y = {{\sqrt 3 } \over 3}\cos t \cr z = {{\sqrt 3 } \over 3}\sin t\cr} \right.(0 \le t \le 2\pi )$$

    • 2

      【单选题】化简 sin( x + y )sin( x - y ) + cos( x + y )cos( x - y ) 的结果是 A. sin 2 x B. cos 2 y C. - cos 2 x D. -cos 2 y

    • 3

      【单选题】()把x、y定义成float类型变量,并赋同一初值3.14。 A. float x, y=3.14; B. float x, y=2*3.14; C. float x=3.14, y=x=3.14 ; D. float x=y=3.14;

    • 4

      曲线积分$$\int_{(0,0}^{(x,y)}(2x\cos y-y^2\sin x)dx+(2y\cos x-x^2\sin y)dy=$$ A: $y^2\cos x+x^2\cos y$ B: $x^2\cos x+y^2\cos y$ C: $x^2\sin y+y^2\sin x$ D: $x^2\sin x+y^2\sin y$