(m+n)^2+(m-n)^2=2(m^2+n^2)
m,n满足x^2+y^2=1,故m^2+n^2=1,
(m+n)^2+(m-n)^2=2
P(m+n,m-n)的轨迹方程(m+n)^2+(m-n)^2=2
即
P(x,y)的轨迹方程x^2+y^2=2
半径为根号2的圆.
(m+n)^2+(m-n)^2=2(m^2+n^2)
m,n满足x^2+y^2=1,故m^2+n^2=1,
(m+n)^2+(m-n)^2=2
P(m+n,m-n)的轨迹方程(m+n)^2+(m-n)^2=2
即
P(x,y)的轨迹方程x^2+y^2=2
半径为根号2的圆.