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: $y_{1}=0.005cos(314t+3.14x),y_{2}=0.005cos(314t-3.14x);$
举一反三
- 设函数$$y=y(x)$$由$$\left\{ \begin{matrix} x=a(t-\sin t), \\ y=a(1-\cos t) \\ \end{matrix} \right.$$确定,则$${y}''(x)=$$(). A: $$-\frac{1}{a(1-\cos t)}$$ B: $$-\frac{1}{a{{(1-\cos t)}^{2}}}$$ C: $$\frac{1}{a(1-\cos t)}$$ D: $$\frac{1}{a{{(1-\cos t)}^{2}}}$$
- 设\(z = f(x,y)\),\(x = \sin t\),\(y = {t^3}\),则全导数\( { { dz} \over {dt}} = \) A: \({f'_x} \sin t+ 3{t^2}{f'_y}\) B: \({f'_x} \cos t+ {t^2}{f'_y}\) C: \({f'_x} \cos t+ 3{t^2}{f'_y}\) D: \({f'_y} \cos t+ 3{t^2}{f'_x}\)
- 一空间曲线由参数方程x=t y=sin(2t) , -3<t<3z=cos(3t*t)表示,绘制这段曲线可以由下列哪组语句完成。 A: t=-3:0.1:3;x=t;y=sin(2*t);z=cos(3*t.*t);plot3(x, y, z, t) B: t=-3:0.1:3;x=t;y=sin(2*t);z=cos(3*t*t);plot3(x, y, z) C: t=-3:0.1:3;y=sin(2*t);z=cos(3*t.*t);plot3(x, y, z) D: t=-3:0.1:3;x=t;y=sin(2*t);z=cos(3*t.*t);plot3(x, y, z) E: x=-3:0.1:3;y=sin(2*x);z=cos(3*x.*x);plot3(x, y, z)
- 求解常微分方程组<img src="http://img1.ph.126.net/B8qMozAYz7oEzmWV3LBSvg==/6597340246519736485.png" />, 应用的语句是? DSolve[{x'[t]+y[t]==Cos[t],y'[t]+x[t]==Sin[t]},{x,y},t]|DSolve[{x'[t]+y[t]==Cos[t],y'[t]+x[t]==Sin[t]},x[t],y[t],t]|DSolve[{x'[t]+y[t]==Cos[t],y'[t]+x[t]==Sin[t]},{x[t],y[t]},t]|DSolve[x'[t]+y[t]=Cos[t],y'[t]+x[t]=Sin[t],{x[t],y[t]},t]
- 一空间曲线由参数方程x=ty=sin(2t) , -3<t<3z=cos(3t*t)表示,绘制这段曲线可以由下列哪组语句完成。? t=-3:0.1:3;x=t;y=sin (2*t);z=cos (3*t.*t);plot3(x, y, z)|t=-3:0.1:3;x=t;y=sin (2*t);z=cos (3*t*t);plot3(x, y, z)|t=-3:0.1:3;y=sin (2*t);z=cos (3*t.*t);plot3 (x, y, z)|t=-3:0.1:3;x=t;y=sin (2*t);z=cos (3*t.*t);plot3(x, y, z, t)
内容
- 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: $x^2\sin x+y^2\sin y$