求证 cos*xcos*y + sin*xsin*y + sin*xcos*y + xin*ycos*x = 1

求证 cos*xcos*y + sin*xsin*y + sin*xcos*y + xin*ycos*x = 1 (2xsin(y/x)-ycos(y/x))dx+(xcos(y/x)+1)dy=0 求y 求证:sin(x-y)sin(x+y)/sin²xcos²y=1-cot²xtan ycos(y/x)=((x^2/y)*sin(y/x)+xcos(y/x))dy/dx 请问这道题该用什么方法解 如果代 xcosΩ/a+ysinΩ/b=1,xsinΩ/a-ycosΩ/b=1 求证：x^2/a^2+y^2/b^2=1 坐等牛 y=xcos(1/x) 求方程[xcos(x+y)+sin(x+y)]dx+xcos(x+y)dy=0的通解, 求函数y=2sin xcos x+2sin x+2cos x+4的值域 求证 sinˇ4X+sin²Xcos²X+cos²X = 1 求解微分方程 (x-ycos(y/x))dx+xcos(y/x)dx=0 求解微分方程：[x-ycos(y/x)]dx+xcos(y/x)dy=0. 求函数y=sin^4x+cos^4x+4sin^2xcos^2x-1的最小正周期和值域