CORE Coordinate Geometry and Transformations - New Indian ...

So, the coordinates of P‟ (x‟, y‟) will given by
x‟ = - x
y‟ = y (x, y) (-x, y)
We say that P‟ (-x, y) is the reflection of the point P(x, y) in y-axis
Thus, reflection of the point (-3, -4) in y-axis will be (-3, 4). Similarly, reflection of the
point (3, -4) in y-axis will be (-3, -4) and reflection of the point (-2, -5) in y axis is
[-(-2), -5)] i.e,. (2, -5) and so on.
(iii) Reflection in the line x = constant, say x = a
Fig. 17
Clearly x = a is a line parallel to y-axis. (See Fig.21)
Let P(x, y) be any point.
If we consider line x = a as a plane mirror, the image P‟ of the point P will be at the same
distance as P is from the line x = a. i.e., PM = P‟M.
So, the coordinates of P‟ (x‟, y‟) will be given by
x – a = a – x‟ i.e., x‟ = 2a – x
and y‟ = y (x, y) (2a-x, y)
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