Method of Variation of Parameter
Method of Variation of Parameter:
This method is very useful in finding the general solution of the second order equation.
The complementary function of (1)
C.F = c1f1 c2f2
Where c1,c2 are constant and f1 and f2 are function of x.
Then, P.I = Pf1 Qf2
∴ y = c1f1 c2f2 P.I
1. Solve (D2 4)y = sec2x
Solution: The A.E is m2 4 = 0
m = ±2i
C.F = C1cos2x C2sin2x