A ray of light passing through the point (1, 2) reflects on the x-axis at point A and the reflected ray passes through the point (5, 3). Find the coordinates of A.



Let the coordinate of point A be (a, 0)


Draw a line (AL) perpendicular to the x –axis.


We know that angle of incidence is equal to angle of reflection. Hence, let


<BAL = <CAL = ɸ


Let <CAX = Ɵ


Therefore,


<OAB = 1800 –(Ɵ+2ɸ) = 1800 –[Ɵ+2(900 - Ɵ)]


= 1800 Ɵ+1800 +2Ɵ


= Ɵ


Thus, <BAX = 1800 Ɵ


Now, slope of line AC =


------------ (1)


Slope of line AB =




----------------- (2)


From equations (1) and (2), we get,



3a – 3 = 10 – 2a


a =


Therefore, the coordinates of point A are .


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