已知α是第三象限角，且sin α＝[img=24x33]17da42543a9ab7e.jpg[/img]，则3cos α＋4tan α＝( )
未知类型：{'options': ['', ' [img=21x20]17da3b4bbe936ec.jpg[/img]', ' [img=31x20]17da428bf661b9c.jpg[/img]', ' [img=21x19]17da40123055a99.jpg[/img]'], 'type': 102}
未知类型：{'options': ['', ' [img=21x20]17da3b4bbe936ec.jpg[/img]', ' [img=31x20]17da428bf661b9c.jpg[/img]', ' [img=21x19]17da40123055a99.jpg[/img]'], 'type': 102}
举一反三
- 求不定积分[img=132x48]17da6537fc8dad6.png[/img]； （ ） A: -(4*(cos(x/2)/2 + 2*sin(x/2)))/(17*exp(2*x)) B: (4*(sin(x/2)/2 + 2*sin(x/2)))/(17*exp(2*x)) C: (4*(cos(x/2)/2 + 2*sin(x/2)))/(17*exp(2*x)) D: (4*(cos(x/2)/2 + 2*cos(x/2)))/(17*exp(2*x))
- 求微分方程[img=143x21]17da5f14490e50e.png[/img]的通解,实验命令为(). A: dsolve(D2y-2*Dy+5*y=sin(2*x),x)ans =exp(x)*sin(2*x)*C2+exp(x)*cos(2*x)*C1+1/17*sin(2*x)+4/17*cos(2*x) B: dsolve('D2y-2*Dy+5*y=sin(2*x)','x')ans =cos(2*x)*(sin(4*x)/17 - cos(4*x)/68 + 1/4) - sin(2*x)*(cos(4*x)/17 + sin(4*x)/68) + C1*cos(2*x)*exp(x) - C2*sin(2*x)*exp(x) C: dsolve(D2y-2*Dy+5*y=sin(2*x),'x','y')ans =exp(x)*sin(2*x)*C2+exp(x)*cos(2*x)*C1+1/17*sin(2*x)+4/17*cos(2*x)
- 角[img=9x11]17da3e984030960.jpg[/img]终边在直线y=3x上且是第三象限角，则[img=31x11]17da5c98b172fb7.jpg[/img] 未知类型：{'options': ['', ' [img=24x33]17da42543a9ab7e.jpg[/img]', ' [img=46x37]17da60e01a3723d.jpg[/img]', ' [img=54x37]17da60e023170b3.jpg[/img]'], 'type': 102}
- 已知随机变量X的分布列如下：[img=386x130]17e43ec4c459e73.png[/img]，则E(X)= A: 17/30 B: m未知，无法求出 C: -30/17 D: -17/30
- 若X服从参数λ=[img=11x33]17e43ef9aafbb94.jpg[/img]的指数分布，则P{3 <;x<;9}=() 未知类型：{'options': ['', ' [img=105x56]17e444c8e04c501.png[/img]', ' [img=66x49]17e444c8eac1d76.png[/img]', ' [img=69x47]17e444c8f4eafd9.png[/img]'], 'type': 102}