3 variable limit problem.sighs

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Homework Help Overview

The problem involves evaluating the limit of the expression [sin (x^2 + y^2 + z^2)] / [(x^2 + y^2 + z^2)^(1/2)] as the variables x, y, and z approach 0. The subject area pertains to multivariable calculus and limits.

Discussion Character

  • Exploratory, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • Participants discuss using the limit of sin(θ)/θ as θ approaches 0. Some suggest substituting u = x^2 + y^2 + z^2 and exploring the limit as u approaches 0. There is mention of applying L'Hôpital's rule and manipulating the expression to facilitate evaluation.

Discussion Status

There are multiple attempts to analyze the limit, with some participants expressing uncertainty about their approaches. Guidance has been offered regarding the substitution and manipulation of the expression, but no consensus has been reached on the correctness of the methods discussed.

Contextual Notes

Participants indicate that this is a homework assignment, and there is a sense of seeking clarification and support in understanding the problem. Some express gratitude for responses received, highlighting a collaborative atmosphere.

iamyes
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Homework Statement



Determine whether the following limit exist. If so, find its value

[sin (x^2 + y^2 + z^2 )] / [(x^2 + y^2 + z^2)^1/2)]
as x,y,z approach 0,0,0


The Attempt at a Solution



i tried to do using the limit of sin Ѳ / Ѳ as Ѳ approaching 0

im from malaysia and this is my assignment question and i can't figure out the way to solve this question
 
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I'm not sure if this is right, but here's my attempt:
Let u = x^2 + y^2 + z^2
limit of u approaching 0 of [sin u] / [u^.5]
sin(0) / [0^.5] = 0/0

Therefore, you can use L'hopital's rule.
sin u / u^.5
cos u / .5u^(-.5)
2cos u / (1/u^.5)
2cos u (u^.5)
u = x^2 + y^2 + x^2 = 0 so 2cos(0)(0) = 0.
 
hey thanks for ur reply!
im not sure if its correct cos i don't know either! =)
but, a million thanks to u for replying!

anyone have some more opinions?
i wud love to discuss more about this =)
 
iamyes said:

Homework Statement



Determine whether the following limit exist. If so, find its value

[sin (x^2 + y^2 + z^2 )] / [(x^2 + y^2 + z^2)^1/2)]
as x,y,z approach 0,0,0


The Attempt at a Solution



i tried to do using the limit of sin Ѳ / Ѳ as Ѳ approaching 0

im from malaysia and this is my assignment question and i can't figure out the way to solve this question
As you say, with [itex]u= x^2+ y^2+ z^2[/itex],
[tex]\frac{sin(x^2+y^2+ z^2)}{(x^2+ y^2+ z^2)^{1/2}}= \frac{sin(u^2)}{u}[/tex]
Multiply both numerator and denominator by u to write that as
[tex]u\frac{sin(u^2)}{u^2}[/tex]
and now use [itex]sin(\theta)/\theta[/itex].
 
HallsofIvy said:
As you say, with [itex]u= x^2+ y^2+ z^2[/itex],
[tex]\frac{sin(x^2+y^2+ z^2)}{(x^2+ y^2+ z^2)^{1/2}}= \frac{sin(u^2)}{u}[/tex]
Multiply both numerator and denominator by u to write that as
[tex]u\frac{sin(u^2)}{u^2}[/tex]
and now use [itex]sin(\theta)/\theta[/itex].

thanks a lot dat really makes my day both of u gave me the same way of solutions and i think it is the best solution
thanks!
 

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