If a triangle is inscribed in a rectangular hyperbola, its orthocentre lies
on the curve
Let rectangular hyperbola
xy=c2..........(i)
Let three points on Eq. (i) are
A(ct1,ct1),B(ct2,ct2),A(ct3,ct3)
Let orthocentre is P(h,k) then slope of AP × slope of BC =-1
⇒k−ct1h−ct1×ct3−ct2ct3−ct2=−1⇒k−ct1h−ct1×−1t2t3=−1⇒k−ct1=ht2t3−ct1t2t3..................(ii)Similarly,BP⊥ACthen k−ct2=ht3t1−ct1t2t3.................(iii)
Subtracting Eq. (iii) from Eq. (ii), then we get h=−ct1t2t3
Substituting the value h in Eq. (ii) then k=−ct1t2t3
∴ Orthocentre is (−ct1t2t3,−ct1t2t3)
which lies on xy=c2