设a0(x,y) 因为垂直 =>(x,y).(3,4) =0 3x+4y=0 |a0|=1 (单位向量) =>x^2+y^2=1 x^2 + 9x^2 /16 =1 25x^2/16 =1 x =4/5,y = -3/5 x =-4/5,y = 3/5 a0= (4/5,-3/5) or (-4/5,3/5)
