Question

Prove that the length of focal cord having parameters t1 and t2 for its end points is (t2-t1)^2

Answer 1

Answer:

Y∧2 = 4ax

t1t2 = 1

AB = AS + BS

     = at12 +a + at22 + a

     = a(t12 + t22 + 2)

     =  a( t12 + 1/t1 + 2)

     = a( t1 +1/t1)^2