Mathematics
Points (8, 0) and (-3, 0) are invariant points under reflection in the line L1, points (0, -9) and (0, 5) are invariant points under reflection in the line L2.
(i) Name or write down equations of the lines L1 and L2.
(ii) Write down the images of points P(3, 5) and Q(-8, 3) after reflection in line L1. Name the images as P' and Q' respectively.
(iii) Write down the images of P and Q on reflection in L2. Name the images as P" and Q" respectively.
(iv) Describe a single transformation that maps P' to P".
Reflection
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Answer
(i) We know that,
Points are invariant in the line on which they lie.
Given,
(8, 0) and (-3, 0) are invariant points under reflection in the line L1.
Points (8, 0) and (-3, 0) lie on x-axis.
∴ L1 = x-axis.
(0, -9) and (0, 5) are invariant points under reflection in the line L2.
Points (0, -9) and (0, 5) lie on y-axis.
∴ L2 = y-axis.
Hence, L1 = x-axis or y = 0 and L2 = y-axis or x = 0.

(ii) From graph,
Co-ordinates of P' = (3, -5) and Q' = (-8, -3).
(iii) From graph,
Co-ordinates of P" = (-3, 5) and Q" = (8, 3).
(iv) From graph,
The single transformation that maps P' to P" is reflecting in origin.
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