The normal to the rectangular hyperbola xy=c2 at the point 't1' meets the curve again at the point 't2'. Then the value of t31t2is
-1
Normal at t1 meets the curve agiain at t2.
So, the normal passes through (ct1,ct1) and (ct2,ct2)
slope of normal = ct2−ct1ct2−ct1=−1t1t2
Also equation of normal at 't1' is
xt31−yt1−ct41+c=0
∴ Slope of normal = t21=−1t1t2
∴t31t2=−1