In figure, XP and XQ are two tangents to a circle with center O from a point X outside the circle. ARB is tangent to circle at R. Prove that XA + AR = XB + BR.
As the lengths of tangents drawn from an external point to a circle are equal.
XP = XQ
XA + AP = XB + BQ …..(i)
Also BQ = BR and AR = AP
Substituting in (i)
XA + AR = XB + BR
Hence proved.