Find the condition that the chord of contact of tangents from the point `(alpha, beta)` to the circle `x^2 + y^2 = a^2` should subtend a right angle at the centre. Hence find the locus of `(alpha, beta)`.

Answer

`=>a^(2)-h^(2)+a^(2)-k^(2)=0orh^(2)+k^(2)=2a^(2)`