1.

solution of the equation `(dy)/(dx)+1/x tany=1/x^2 tanysiny` isA. ` 2x= (1-2Cx^(2))sin y`B. `x=(1-2 Cx^(2)) sin y`C. `2x = (1+2Cx^(2))sin y`D. None of these

Answer» Correct Answer - d
The given differential equation can be rewritten as ` cot y "cosec" y (dy)/(dx) +1/x "cosec" y = 1/(x^(2))`
On putting ` v = - "cosec" y and (dv)/(dx) = "cosec" y cot y (dy)/(dx),`
we get ` (dv)/(dx) -1/x v = 1/(x^(2))`
which is linear differential equation in v.
Here, `P = -1/x and Q = 1/(x^(2))`
` :. IF = e^(int Pdx)= e^(int - 1/xdx)= e^(-logx)=1/x`
Required solution is
` v = 1/x = int 1/x * 1/(x^(2))dx +C = -1/(2x^(2))+C`
` rArr 2x = (1- 2Cx^(2) ) sin y `


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