A luminous point P is inside a circle.
A ray emanates from P and after two
reflections by the circle,returns to P.
If θ be the angle of incidence, a= the
distance of P from the centre of the
circle and b=the distance of the centre
from the point where the ray in its
course crosses its diameter through P.
prove that tan θ=((a−b)/(a+b))
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