Solving a Simple Differential Equation: y' = (x + xy^2)

Click For Summary
The discussion focuses on solving the differential equation y' = (x + xy^2). The user successfully integrates the equation to arrive at arctan(y) = 0.5x^2 + C. The main challenge is simplifying this expression to isolate y in the form y = ... The conversation highlights the relationship between the tangent and arctangent functions, noting that tan(arctan(x)) = x is valid within specific bounds. Understanding these bounds is crucial for correctly expressing y in terms of x.
S[e^x]=f(u)^n
Messages
23
Reaction score
0

Homework Statement


i'm trying to solve the simple differential equation y'=(x+xy^2)


2. The attempt at a solution

i get dy/(1+y^2)=xdx and then integrate over the whole thing getting the solution

arctan(y)=0.5x^2+C

my problem is how do i simply this down to an equation in the form y=...

i must be missing something
 
Physics news on Phys.org
S[e^x]=f(u)^n;1635559 said:

Homework Statement


i'm trying to solve the simple differential equation y'=(x+xy^2)


2. The attempt at a solution

i get dy/(1+y^2)=xdx and then integrate over the whole thing getting the solution

arctan(y)=0.5x^2+C

my problem is how do i simply this down to an equation in the form y=...

i must be missing something
well remember that if tan(x)=y then arctan(y)=x does this help u? Tan and arctan are inverse functions so, tan(arctan x)=x
 
Last edited:
but that x only valid under certain bounds right? and I'm having trouble figuring out what those are
 
Question: A clock's minute hand has length 4 and its hour hand has length 3. What is the distance between the tips at the moment when it is increasing most rapidly?(Putnam Exam Question) Answer: Making assumption that both the hands moves at constant angular velocities, the answer is ## \sqrt{7} .## But don't you think this assumption is somewhat doubtful and wrong?

Similar threads

  • · Replies 8 ·
Replies
8
Views
2K
  • · Replies 7 ·
Replies
7
Views
1K
Replies
7
Views
2K
Replies
3
Views
2K
Replies
10
Views
2K
  • · Replies 25 ·
Replies
25
Views
2K
Replies
9
Views
2K
  • · Replies 7 ·
Replies
7
Views
2K
  • · Replies 27 ·
Replies
27
Views
2K
  • · Replies 4 ·
Replies
4
Views
2K