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| | Coordinates--lesson plan #9 |
 | | Optional--extending this to (x,y,z) coordinates in 3-dimensional space, to (r,φ) plane polar coordinates and to 3-dimensional polar coordinates (r,θ, λ). |
 | | The coordinates x and y are defined as before, in some plane, and z is measured from the origin in a direction perpendicular to the (x,y) plane. |
 | | Polar coordinates also have an "origin" O as reference point, but instead of (x,y), they use the distance r from O to the given point P, and the angle φ ("phi"--Greek f) between the line OP ("radius"--hence the letter "r") and some reference line. |
| www-istp.gsfc.nasa.gov /stargaze/Lcelcoor.htm (1578 words) |
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