example of derivative as parameter
For solving the (nonlinear) differential equation
(1) |
with , according to III in the parent entry (http://planetmath.org/DerivativeAsParameterForSolvingDifferentialEquations), we differentiate both sides in regard to , getting first
Removing the denominators, we obtain
The left hand side can be factored:
(2) |
Now we may use the zero rule of product; the first factor of the product in (2) yields , i.e.
whence , i.e. . Substituting this into the original equation (1) we get . Hence the general solution of (1) may be written
The second factor in (2) yields , which is substituted into (1) multiplied by :
Thus we see that , which is again set into (1), giving
Finally, we can write it
which (a variant of the so-called semicubical parabola) is the singular solution of (1).