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Differential Equations

Question
CBSEENMA12033139

Solve:
dy over dx space equals straight y over straight x plus tan straight y over straight x open parentheses 0 less than straight y over straight x less than straight pi over 2 close parentheses

Solution

The given differential equation is
                   dy over dx space equals space straight y over straight x plus tan straight y over straight x space space space space space space space space space space space space open parentheses 0 less than straight y over straight x less than straight pi over 2 close parentheses                ...(1)
Put y = v x so that dy over dx equals straight v plus straight x dv over dx
therefore space space space space from space left parenthesis 1 right parenthesis comma space space straight v plus straight x dv over dx space equals space straight v plus tan space straight v space space or space space space straight x dv over dx space equals space tan space straight v space space or space space space fraction numerator 1 over denominator tan space straight v end fraction dv space equals space dx over straight x
or      integral cot space straight v space dv space equals space integral dx over straight x
or     log space open vertical bar sin space straight v close vertical bar space equals space log space open vertical bar straight x close vertical bar space plus space log space open vertical bar straight c close vertical bar space space or space space space log space open vertical bar sin space straight v close vertical bar space equals space log space open vertical bar cx close vertical bar
or       sin space straight v space equals space cx space space space space or space space space space space sin straight y over straight x space equals space space straight c space straight x space is space the space required space solution. space

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