Math Chapter Wise Ordinary And Partial Differential Equations, Integral Equations And Calculus Of Variations English MCQ UP PCS (Pre) 2005 Q.The orthogonal trajectory of the family of straight lines y = mx, where m is a parameter, is: Ay2 = 4ax Bx2 = 4ay Cx2 +y2 = a2 Dx2 –y2 = a2 Show answer Correct answer: x2 +y2 = a2