coordinate geometry notes class ix

 

π Mark

Mathematics

Notes:-Coordinate Geometry

^{class 9th}

^{Note:- Read carefully the given short notes and sorry for spelling mistakes.}

1.Cartesian coordinates (Ordered pair):- A pair of numbers “x” and “y”

listed in a specific order with

“x”at first place and “y” at second place is called an ordered pair (x,y).

Example :- (1,2) here x=1 and y=2

2.Coordinate axes:- The position of a point in a plane is determined with

reference to two fixed mutually perpendicular lines

called coordinate axes.

(I) Origin:- The point of intersection axes or lines (coor

-dinate axes) is called origin.

(ii) X Axis:- The horizontal line in coordinate axes is know as x axis .

(iii) Y axis:- The vertical line is known as y axis.

(iv)Quadrants:- Four parts divided by axes is called quadrants.

3.Sign Convention:-

Region	Quadrant	Nature of x and y	Signs of coordinates
XOY	I	x>0, y>0	(+,+)
YOX'	II	x<0, y>0	(-,+)
X'OY'	III	x<0, y<0	(-,-)
Y'OX	IV	x>0, y<0	(+,-)

# Some important points

(I) (x,y) is not equal to (y,x).

(ii) The distance of a point from the y-axis is called its x coordinate or

“abscissa” and the distance of a the point from the x-axis is called

its y-coordinate or “ordinate”.

(iii) if the abscissa of a point is x and ordinate of a point is y then (x,y)

are called coordinates of the point.

(iv) The coordinate of a point on x axis are of form (x,0) and that of the

point on y axis are (0,y).

(v) The coordinates of origin are (0,0).

(vi) (x,y)=(y,x) if x =y

“trick to learn which is abscissa and which axis is ordinate”

x-axis = abscissa

y-axis = ordinate

(here “x” comes first and in rhs “a” comes first this is the trick)