1.x²+3y²=6 为椭圆,与x轴焦点为(-√6,0),(√6,0),与y轴焦点为(0,-√2),(0,√2).
xcosa+ysina=2 =>√(x^2+y^2) (x/√(x^2+y^2)cosa+x/√(x^2+y^2)sina)=√(x^2+y^2) sin(b+a)=2
sin(b+a)=2/√(x^2+y^2),因-1≤sin(b+a)≤1,故0