Posted by Soroban on September 23, 2002 at 14:14:14:
In Reply to: 2nd order linear DE... need help. (Prob #2) posted by colin on September 23, 2002 at 11:17:22:
: I'm also at an impasse on this prob:
: yy'' + (y')^2 = 0
: let v = y'
: dv/dt = y'' = (dv/dy)(dy/dt) = v(dv/dy)
: yv(dv/dy) + v^2 = 0
: dv/dy = -v/y
: dv/v = - dy/y
: ln(v) = -ln(y) + c1
Here it is, Colin! A little mishandling of logs.
ln(v) = -ln(y) + ln(C)
ln(v) = ln(C/y)
v = C/y
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