Math Help - Can any one solve this diff eqn?

1. Can any one solve this diff eqn?

dy/dx=sin(x+y)+cos(x+y)
I’v tried substituting (x+y)=z, but I don’t think its gonna work. Can anyone help?
Also,
tan^-1(dy/dx)=x+y
I'v tried dy/dx=tan(x+y), substituting x+y=z.

2. Originally Posted by sverbinayak
dy/dx=sin(x+y)+cos(x+y)
I’v tried substituting (x+y)=z, but I don’t think its gonna work. Can anyone help?
Also,
tan^-1(dy/dx)=x+y
I'v tried dy/dx=tan(x+y), substituting x+y=z.
Why do you think substituting $z = x + y$ won't work? Did you actually try doing it? Please show what you get and where you're stuck.