若x.y属于（0,π/2）cos(x-y/2)=根号3/2sin(x/2-y)=-1/2则cos(x+y)=
举一反三
- 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: ${{x}^{2}}\cos y+{{y}^{2}}\cos x+C$
- 以下表达式中，有两个的计算结果是相同的，请挑选出来 A: 1 / sqrt(sin(x) * sin(x) + cos(y) * cos(y)) B: sqrt(pow(sin(x), 2) + pow(cos(y), 2)) C: pow(sin(x) * sin(x) + cos(y) * cos(y), 0.5) D: pow(pow(sin(x), 2) + pow(cos(y), 2), 2)
- 在区域<img src="http://img2.ph.126.net/gYKpVz-ihv2c735JpXLFXA==/148900262780427590.png" />画出函数<img src="http://img1.ph.126.net/1MufBuQ2l1d-e3P0WpTtOA==/6597356739194210350.png" />的密度图形。? ContourPlot[Sin[x^2]+y Cos[y^2],{x,-6,6},{y,-6,6}]|DensityPlot[Sin[x^2]+y Cos[y^2],{x,-6,6},{y,-6,6}]|DensityPlot[Sin[x^2]+y Cos[y^2],{x,-6,6},{y,-6,6}]|ContourPlot[Sin[x^2]+y Cos[y^2],{x,-6,6},{y,-6,6}]