Thursday, 14 November 2013

`y' + ytanx = secx + cosx , y(0) = 1` Find the particular solution of the differential equation that satisfies the initial condition


Given` y'+ytanx=secx+cosx`


when the first order linear ordinary Differentian equation has the form of


`y'+p(x)y=q(x)`


then the general solution is ,


`y(x)=((int e^(int p(x) dx) *q(x)) dx +c)/ e^(int p(x) dx)`


so,


`y'+ytanx=secx+cosx--------(1)`


`y'+p(x)y=q(x)---------(2)`


on comparing both we get,


`p(x) = tanx and q(x)=secx +cosx`


so on solving with the above general solution we get:


y(x)=`((int e^(int p(x) dx) *q(x)) dx +c)/e^(int p(x) dx)`


=`((int e^(int (tanx) dx) *(secx+cosx)) dx +c)/e^(int tanx dx)`


first we...



Given` y'+ytanx=secx+cosx`


when the first order linear ordinary Differentian equation has the form of


`y'+p(x)y=q(x)`


then the general solution is ,


`y(x)=((int e^(int p(x) dx) *q(x)) dx +c)/ e^(int p(x) dx)`


so,


`y'+ytanx=secx+cosx--------(1)`


`y'+p(x)y=q(x)---------(2)`


on comparing both we get,


`p(x) = tanx and q(x)=secx +cosx`


so on solving with the above general solution we get:


y(x)=`((int e^(int p(x) dx) *q(x)) dx +c)/e^(int p(x) dx)`


=`((int e^(int (tanx) dx) *(secx+cosx)) dx +c)/e^(int tanx dx)`


first we shall solve


`e^(int (tanx) dx)=e^(ln(secx))= secx `     


so proceeding further, we get


`y(x) =((int e^(int (tanx) dx) *(secx+cosx)) dx +c)/e^(int tanx dx)`


=`((int secx *(secx+cosx)) dx +c)/(secx )`


=`((int (sec^2 x+cosxsecx)) dx +c)/(secx )`


= `((int (sec^2 x)dx +int 1 dx) +c)/secx`

=` (tanx+x +c)/secx`


=` sinx +(x+c)/secx`


`y(x) = sinx +(x+c)/secx`




to find the particular solution of the differential equation we have `y(0)=1`



on substituting x=0 we get y=1 and so we can find the value of the c


`y(0)= sin0+(0+c)/sec0 =0+0+c/1 = c`


but `y(0)=1`


=> `1=c`


=> `c=1 `


so `y=sinx+(x+1)/secx` 

No comments:

Post a Comment