I am trying to solve the differential equation e^x*y[x]+Sec[x]*y'[x]+y''[x]==0 with DSolve. However, the ouput is the same as the input which usually means an error has occured. I'm sure my syntax is correct since I used DSolve for many equations before this and had success. Is there something that makes this function not work with DSolve?
Also, I tried using NSolve and it said that y was an interpolating function from 0 to 0 and <>. I would assume that this is a special type of function in mathematica but what is the formula for the equation? (i.e y = x^2 + 5 ) Thanks for the help.