Find all functions f(x) defined on ( &#x2212;<!-- - --> &#x03C0;<!-- π --> 2 </mfr

Simone Werner

Simone Werner

Answered question

2022-05-22

Find all functions f(x) defined on ( π 2 , π 2 ) which has a primitive F(x) such that
f ( x ) + cos ( x ) F ( x ) = sin ( 2 x ) ( 1 + sin ( x ) ) 2 .
Hence F satisfies a first order linear differential equation in F with integrating factor e sin ( x )
So i have to integrate
2 e sin ( x ) sin ( x ) cos ( x ) ( 1 + sin ( x ) ) 2 .
By putting t = sin ( x ), it reduces to t e t ( 1 + t 2 ) but now I am not getting it.

Answer & Explanation

thoumToofwj

thoumToofwj

Beginner2022-05-23Added 16 answers

Note that you have to integrate t e t ( 1 + t ) 2 which yields e t ( 1 + t ) .
Hence we obtain
F ( x ) = 2 1 + sin ( x ) + C e sin ( x )
and f ( x ) = F ( x )

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