Question
Form the differential equation of the family of curves by eliminating arbitrary constants a and b.
y = ex (a cosx + b sinx)
Solution
The given equation is
y = ex (a cosx + b sinx) ...(1)
Differentiating both sides w.r.t x, we get

or
...(2)

Again differentiating w.r.t x,

or
or

or
, which is required differential equation.
y = ex (a cosx + b sinx) ...(1)
Differentiating both sides w.r.t x, we get

or


Again differentiating w.r.t x,

or

or


or
