Ronald L. answered 12/10/20
Life-long Engineer: 20+ years practicing then 20+ years teaching
Standard 2-dimension vector notation (magnitude @ angle) would show the location as 10 @ -60 degree, that is, an arrow of length 10 pointing downward from horizontal and to the right of vertical such that the angle between the magnitude arrow and the horizontal is 60 degrees. In standard rectangular coordinates this would convert to (5, -8.66), i.e., 10 x [cos (-60), sin(-60)].