Verifying Relations: Solving x^2 + y^2 = 1 | Homework Help

  • Thread starter bengaltiger14
  • Start date
  • Tags
    Relations
In summary, the relation x2+y2=1 is not a solution to the differential equation: dy/dx=xy/(x^2-1). To solve for dy/dx in the equation, make dy/dx the subject of the equation.
  • #1
bengaltiger14
138
0

Homework Statement


Verify that the relation x^2 + y^2 = 1 is a solution to the differential equation:
dy/dx = xy/(x^2 - 1)

Can anyone point me in the right direction on how to begin to solve this problem? Do I take integral of the DE and just plug into equation?
 
Last edited:
Physics news on Phys.org
  • #2
You could take x^2 + y^2 = 1 and find dy/dx and see if it is the same as the DE
 
  • #3
dy/dx is just 2x+2y. So it does not equal correct?
 
  • #4
bengaltiger14 said:
dy/dx is just 2x+2y. So it does not equal correct?

2x+2y(dy/dx)=0 is what you get when you differentiate implicitly with repect to x. Now just find dy/dx and do a bit of algebra.
 
  • #5
I'm sorry but I'm really slow at DE's.

2x+2y(dy/dx)=0

What do you mean find dy/dx. I thought dy/dx was 2x+2y=0.

Are you saying to solve for dy/dx in the first equation?
 
  • #6
bengaltiger14 said:
Are you saying to solve for dy/dx in the first equation?

Yes, make dy/dx the subject of the equation.

EDIT: is the relation supposed to be y2-x2=1 ?
 
Last edited:
  • #7
2y(dy/dx) = -2x

divide by 2y:

dy/dx = -2x/2y
 
  • #8
bengaltiger14 said:
2y(dy/dx) = -2x

divide by 2y:

dy/dx = -2x/2y

So dy/dx= -x/y right?

Now multiply the numerator and denominator by y.

(Forget my edit in the previous post)
 
  • #9
dy/dx = -xy

That is the answer to the problem? So the DE is not a solution.
 
  • #10
bengaltiger14 said:
dy/dx = -xy

That is the answer to the problem? So the DE is not a solution.

If dy/dx=-x/y and you multiply by y/y, do you really get dy/dy=-xy or -xy/y2?
 
  • #11
yeah, your right... dy/dx = -xy/y^2

But the top y would just cancel and the y^2 would become y again so why do that?
 
  • #12
bengaltiger14 said:
yeah, your right... dy/dx = -xy/y^2

But the top y would just cancel and the y^2 would become y again so why do that?

Don't cancel out anything. Keep it the way it is. Now from the relation x2+y2=1, what is y2 equal to?
 
  • #13
y^2 = 1-x^2
 
  • #14
bengaltiger14 said:
y^2 = 1-x^2

Now in the equation

[tex]\frac{dy}{dx}=\frac{-xy}{y^2}[/tex]


Replace y2.
 
  • #15
dy/dx = -xy/1-x^2

So they do equal. If you multiply by -1, it gives the DE.
 
  • #16
bengaltiger14 said:
dy/dx = -xy/1-x^2

So they do equal. If you multiply by -1, it gives the DE.

and if it gives the DE, it is a solution of it.
 
  • #17
Cool..Thank you very much for your help and patience.
 

FAQ: Verifying Relations: Solving x^2 + y^2 = 1 | Homework Help

What is the equation x^2 + y^2 = 1 used for?

The equation x^2 + y^2 = 1 is used to describe a circle with a radius of 1 centered at the origin on a graph. It is also known as the unit circle and is often used in trigonometry and geometry.

How do you verify if a given point is on the graph of x^2 + y^2 = 1?

To verify if a point (x,y) is on the graph of x^2 + y^2 = 1, simply substitute the values of x and y into the equation. If the equation holds true, then the point is on the graph. If the equation does not hold true, then the point is not on the graph.

What are the possible solutions for x^2 + y^2 = 1?

The possible solutions for x^2 + y^2 = 1 are an infinite number of points that lie on the circle described by the equation. This includes points with integer coordinates, decimal coordinates, and even irrational coordinates.

Can you use the equation x^2 + y^2 = 1 to solve for either x or y?

Yes, the equation x^2 + y^2 = 1 can be solved for either x or y by isolating the variable and taking the square root of both sides. However, it is important to note that there will be two possible solutions for each variable due to the nature of the equation representing a circle.

How is the equation x^2 + y^2 = 1 related to the Pythagorean theorem?

The equation x^2 + y^2 = 1 is a special case of the Pythagorean theorem, where the length of the hypotenuse of a right triangle is equal to 1. This can be seen by rearranging the terms in the equation to x^2 + y^2 = c^2, where c represents the length of the hypotenuse. This relationship is often used in geometry and physics to solve for unknown lengths or distances.

Back
Top