Let P(x1,y1) be the point of intersection of tangents at the ends of a normal chord of the hyperbola ‌x2∕a2−‌y2∕b2=1. Equation of chord is ‌xx1∕a2−‌yy1/b2=1 b2xx1−a2yy1=a2b2......(i) Equation of a normal chord is ax‌cos‌θ+by‌cot‌θ=a2+b2......(ii) Eqs. (i) and (ii) represent the same line