(ii) the distance measured from O along y-axis in the upward direction (i.e., in the direction OY or in direction parallel to OY) is positive and the distance from y- axis in the downward direction (i.e., in the direction OY’ or in direction parallel to OY’) is negative.īy the above convention of sign the distances along x-axis as well as along y- axis are positive for P, for the point Q, the distance along x-axis is negative and that along x-axis is negative and that along y- axis is positive, for R both these distances are negative and for S the distance along x-axis is positive and that along y is negative.įrom the above discussion it is evident that to determine uniquely the position of a point on a plane referred to mutually perpendicular co-ordinate axes drawn through an origin O we require two signed real numbers. (i) the distance measured from O along x-axis on the right side (i.e., in the direction OX or in direction parallel to OX is positive and the distance from O along x-axis on the left side (i.e., in the direction OX’ or in direction parallel to OX’ is negative To differentiate among the position of such points we introduce the following convention regarding the signs of distances along the co-ordinate axes: Therefore, it is possible to have four different point on the plane of the page at equal distances along the co-ordinate axes. Note that, we shall have points Q, R and S in the second, third and fourth quadrants respectively and the distance of each of them along x-axis and y-axis are 4 and 5 units respectively.
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If OM and MP measure 4 and 5 units respectively then the position of P on the plane is determined i.e., to get the point P on the plane, we are to move from O through a distance of 4 unite along OX and then to proceed through a distance of 5 units in direction parallel to OY. Let P be any point in the first quadrant.