Let \( \Large P \left(x_{1}, y_{1}\right) \) be the point, then the chord of contact of tangents drawn from P to the circle \( \Large x^{2}+y^{2}=a^{2}\ is\ xx_{1}+yy_{1}=a^{2} \) \( \Large \therefore\ x^{2}+y^{2} = a^{2} \left(\frac{xx_{1}+yy_{1}}{a^{2}}\right) \) => \( \Large x^{2}+y^{2}-xx_{1}-yy_{1}=0 \)