Integrating $$\frac{ds}{(2y^2+1)^{3/2}}$$ on a Parabolic Curve

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SUMMARY

The integral $$\int_{C} \frac{ds}{(2y^2+1)^{3/2}}$$ is evaluated over the parabolic curve defined by $$z^2=x^2+y^2$$ and $$x+z=1$$. The parametrization of the curve can be expressed as $$x(t)=\frac{1}{2}-\frac{t^2}{2}$$, $$y(t)=t$$, and $$z(t)=\frac{1}{2}+\frac{t^2}{2}$$, where $$t$$ varies from -1000 to 1000 to cover the entire parabola. The discussion emphasizes the importance of correctly determining the bounds for $$t$$ to ensure accurate computation of the integral.

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Homework Statement



Find $$\int_{C} \frac{ds}{(2y^2+1)^{3/2}}$$
where $$C$$ is the parabola $$ z^2=x^2+y^2 , x+z=1$$

Homework Equations





The Attempt at a Solution


I tried to parametrize the C , s.t$$ x=t, z=1-t, y=\sqrt{2t-1}$$ ,
but it seems to become a mess, and I don't know the bound of t,
and I tried to let$$ x=sin^2ω , z=cos^2ω , y = \sqrt{cos^2ω-sin^2ω}$$
Is $$ω $$from 0 to $$2\pi$$? , but it seems to not easy to compute it.
So I want to know is there any nice method for that Q.?
 
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sigh1342 said:

Homework Statement



Find $$\int_{C} \frac{ds}{(2y^2+1)^{3/2}}$$
where $$C$$ is the parabola $$ z^2=x^2+y^2 , x+z=1$$

Homework Equations





The Attempt at a Solution


I tried to parametrize the C , s.t$$ x=t, z=1-t, y=\sqrt{2t-1}$$ ,
but it seems to become a mess, and I don't know the bound of t,
and I tried to let$$ x=sin^2ω , z=cos^2ω , y = \sqrt{cos^2ω-sin^2ω}$$
Is $$ω $$from 0 to $$2\pi$$? , but it seems to not easy to compute it.
So I want to know is there any nice method for that Q.?

You got:

[tex]z^2=x^2+y^2[/tex]
[tex]z=1-x[/tex]
or:
[tex]x=1/2-y^2/2[/tex]
so we can parameterize that in terms of y as:

[tex]x(y)=1/2-y^2/2[/tex]
[tex]y(y)=y[/tex]
[tex]z=1-(1/2-y^2/2[/tex]
or to make it look nicer:

[tex]x(t)=1/2-t^2/2[/tex]
[tex]y(t)=t[/tex]
[tex]z(t)=1/2+t^2/2[/tex]
and that last parametrization will track a parabolic curve on the surface of [itex]z^2=x^2+y^2[/itex] for how long? Well from one end of the parabola to the other end right? How long is that if I didn't give any end point? How about -100 to 100? Further? How about -1000 to 1000? Further.
 
I got it , thank you very much :D
 

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