Q.

Let y = y(x) be the solution of the differential equation dydx+3(tan2x)y+3y=sec2x, y(0)=13+e3. Then y(π4) is equal to         [2025]

1 43+e3  
2 43  
3 23  
4 23+e3  

Ans.

(2)

Given, dydx+3(tan2x)y+3y=sec2x

 dydx+3(sec2x)y=sec2x

I.F.=e3sec2xdx=e3 tan x

  Solution is given by e3 tan xy=e3 tan xsec2xdx

 e3 tan xy=e3 tan x3+C          ... (i)

  y(0)=13+e3  C=e3

Using equation (i), we get

e3 tan xy=e3 tan x3+e3

  y(π4)=e33+e3e3=43