Let dydx−2ycotx=cosx such that y(π2)=0. If the maximum value of y is k, then the value of k is
A
2
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B
02
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C
2.0
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D
2.00
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Solution
dydx−2ycotx=cosx
This is a linear differential equation in x. I.F.=e−2∫cotxdx=1sin2x
General solution is ysin2x=∫cosxsin2xdx+C ⇒y=−sinx+Csin2x
Since y(π2)=0, therefore C=1 ∴y=sin2x−sinx ⇒y=(sinx−12)2−14 ∴ Maximum value of y is (−1−12)2−14=2