The given differential equations is
d4ydx4−sin(d3ydx3)=0
Since, the higest order derivative which occurs in the given differential equation is d4ydx4. Thus, order of the given equation is 4, as sin(d3ydx3) occurs in the equation is not a polynomial equation. Hence, degree is not defined.
Note:In any differential equation, if a derivative is not in a polynomial equation, then we can find the order but degree cannot be determined.