The correct option is D a1a2+b1b2=0
Assume rectangular hyperbola is xy=c2
Thus equation of tangent and normal at any point 't' are,
xt+ty=2c and y−ct=t2(x−ct)
Now putting y=0 in both the equation we get, a1=2ct,a2=ct−ct3
and putting x=0 we get, b1=2ct,b2=ct−ct3
⇒a1a2+b1b2=2ct(ct−ct3)+2ct(ct−ct3)=0
Hence. option 'C' is correct.