F) =
(
)
1
Q × I F
dy +C
∫
Example 19 Find the general solution of the differential equation 
cos
dy
y
x
dx −
= Solution Given differential equation is of the form
P
Q
dy
y
dx +
=
, where P = –1 and Q  =  cos x
Therefore
I F =
1 dx
x
e
e
  
 
Multiplying both sides of equation by I