【单选题】设z=cos(2x−3y), ()
A. 6cos(2x−3y) B. cos(2x−3y) C. 6sin(2x−3y) D. 6cos(2x+3y)
A. 6cos(2x−3y) B. cos(2x−3y) C. 6sin(2x−3y) D. 6cos(2x+3y)
举一反三
- 已知\( y = {x^3}\cos 2x \)，则\( y'' \)为（ ）. A: 0 B: \( 6x\cos 2x{\rm{ + }}12{x^2}\sin 2x - 4{x^3}\cos 2x \) C: \( 6x\cos 2x - 12{x^2}\sin 2x{\rm{ + }}4{x^3}\cos 2x \) D: \( 6x\cos 2x - 12{x^2}\sin 2x - 4{x^3}\cos 2x \)
- 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: $x^2\sin x+y^2\sin y$
- 【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. $(2x\cos y-{{y}^{2}}\sin x)dx+(2y\cos x-{{x}^{2}}\sin y)dy$的原函数是 ( ) A: ${{x}^{2}}\sin y-{{y}^{2}}\sin x+C$ B: ${{x}^{2}}\sin y+{{y}^{2}}\sin x+C$ C: ${{x}^{2}}\cos y-{{y}^{2}}\cos x+C$ D: ${{x}^{2}}\cos y+{{y}^{2}}\cos x+C$
- 函数\(y = {\sin ^2}x\)的导数为（ ）. A: \(\cos 2x\) B: \(\sin 2x\) C: \( - \sin 2x\) D: \(- \cos 2x\)