已知[img=140x25]1803456980f8212.png[/img]，则二阶导数[img=39x26]1803456989fe38b.png[/img]= ________________。
A: 3-9sin(3t)u(t)
B: 3δ(t)-9sin(3t)u(t)
C: 3δ(t)+9sin(3t)u(t)
D: 3+9sin(3t)u(t)
A: 3-9sin(3t)u(t)
B: 3δ(t)-9sin(3t)u(t)
C: 3δ(t)+9sin(3t)u(t)
D: 3+9sin(3t)u(t)
举一反三
- 已知[img=140x25]1803567cdbdb257.png[/img]，则二阶导数[img=39x26]1803567ce528242.png[/img]= ________________。 A: 3-9sin(3t)u(t) B: 3δ(t)-9sin(3t)u(t) C: 3δ(t)+9sin(3t)u(t) D: 3+9sin(3t)u(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)
- 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)
- 设\(z = {e^{x - 2y}}\)，而\(x = \sin t,\;y = {t^3},\)则\( { { dz} \over {dt}} = \)( ) A: \({e^{\sin t - 2{t^3}}}\) B: \({e^{\sin t - 2{t^3}}}\left( {\cos t - 6{t^2}} \right)\) C: \({e^{\sin t - 2{t^3}}}\ {\sin t } \) D: \({e^{\sin t - 2{t^3}}}\,{t^3}\)
- 求微分方程[img=269x55]17da6536a9fba07.png[/img]的通解； （ ） A: (C15*sin(2*t))/exp(3*t) + (C16*sin(2*t))/exp(3*t) B: (C15*cos(2*t))/exp(3*t) - (C16*sin(2*t))/exp(3*t) C: (C15*cos(2*t))/exp(3*t) + (C16*cos(2*t))/exp(3*t) D: (C15*cos(2*t))/exp(3*t) + (C16*sin(2*t))/exp(3*t)