knockout_artist Messages 70 Reaction score 2 Thread starter Jul 2, 2017 #1 so df/dy' is yy'/ √(1+y'^2) then we are supposed to do y' . [ yy'/ √(1+y'^2) ] - y√(1+y'^2) how does this bring equation 2 in the image ? Attachments 1499007922254.jpeg 21.6 KB · Views: 543
so df/dy' is yy'/ √(1+y'^2) then we are supposed to do y' . [ yy'/ √(1+y'^2) ] - y√(1+y'^2) how does this bring equation 2 in the image ?
formodular Messages 34 Reaction score 18 Jul 2, 2017 #3 Multiply ##f = y \sqrt{1+y'^2}## by ##1 = \frac{\sqrt{1+y'^2}}{\sqrt{1+y'^2}}## then subtract from ##y' f_y'##.
Multiply ##f = y \sqrt{1+y'^2}## by ##1 = \frac{\sqrt{1+y'^2}}{\sqrt{1+y'^2}}## then subtract from ##y' f_y'##.