\
The function is
.
Above equation satisfies the differential equation
.
Find first and second derivatives of the function and substitute those results in above differential equation
\to find A and B.
\
.
Differentiate on each side with respect to
.

Derivative of the sine function:
.
Derivative of the cosine function:
.

Differentiate on each side with respect to
.

Substitute the values of
and
in differential equation
.

\
Compare
and
coefficients respectively.

Solve above two equations to find
and
values.
From equation
, we have
.
Substitute
in
.

Substitute
in
.
.
Thus,
and
.
\
and
.