Differential Equation with an Initial condition

Join the discussion
Ask a follow-up here, or get your own question answered by working scientists, mathematicians and engineers — people, not an autocomplete.
Real named experts · corrections over time · the nuance an AI answer skips
3 replies · 3K views
Zinggy
Messages
12
Reaction score
0

Homework Statement


x(dy/dx) = 3y +x4cos(x), y(2pi)=0

Homework Equations


N/A

The Attempt at a Solution


I've tried a couple different ways to make this separable, but you always carry over a 1/dx or 1/dy term and I can never fully separate this. I've also tried to do a Bernoulli differential equation method by doing a change of variable and putting it in the form: xy'-3y = x4cos(x) but it's not quite the right format to allow that to work, I would need it to be y4cos(x) instead.
 
Physics news on Phys.org
Zinggy said:

Homework Statement


x(dy/dx) = 3y +x4cos(x), y(2pi)=0

Homework Equations


N/A

The Attempt at a Solution


I've tried a couple different ways to make this separable, but you always carry over a 1/dx or 1/dy term and I can never fully separate this. I've also tried to do a Bernoulli differential equation method by doing a change of variable and putting it in the form: xy'-3y = x4cos(x) but it's not quite the right format to allow that to work, I would need it to be y4cos(x) instead.
Divide both sides of the DE by ##x##. That gives a very standard first-order DE with a well-known solution. (Hint: the hint from #2).
 
  • Like
Likes   Reactions: Zinggy
Divide both sides by ##x## and rearrange into:
##\dot y -\frac 3 x y = x^3 cos(x)##
Since you are studying differential equations I trust that you can figure out how to solve this.