3 variable limit problem.sighs

In summary, the problem is to determine the limit of [sin (x^2 + y^2 + z^2)] / [(x^2 + y^2 + z^2)^1/2] as x,y,z approach 0,0,0 and the solution involves using the limit of sin Ѳ / Ѳ as Ѳ approaches 0 and the substitution u = x^2 + y^2 + z^2. The final solution uses the property of sin(\theta)/\theta and the limit is equal to 0.
  • #1
iamyes
9
0

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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  • #2
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.
 
  • #3
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 =)
 
  • #4
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].
 
  • #5
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!
 

FAQ: 3 variable limit problem.sighs

What is a 3 variable limit problem?

A 3 variable limit problem refers to a mathematical problem where three variables (usually x, y, and z) are involved in determining the limit of a function as one or more of the variables approach a certain value.

How do you solve a 3 variable limit problem?

To solve a 3 variable limit problem, you need to first identify the variables and the function involved. Then, you can use techniques such as substitution, factoring, or L'Hopital's rule to simplify the expression and evaluate the limit.

What is the importance of studying 3 variable limit problems?

Studying 3 variable limit problems is important because it helps us understand the behavior of a function as multiple variables approach a certain value. This is useful in fields such as physics, engineering, and economics, where multiple variables are often involved in real-world problems.

Are there any specific techniques or strategies for solving 3 variable limit problems?

Yes, there are several techniques and strategies that can be used to solve 3 variable limit problems. Some of these include using algebraic manipulation, applying the squeeze theorem, or using graphical methods such as plotting the function on a 3D graph.

Are there any common mistakes to avoid when solving 3 variable limit problems?

Yes, some common mistakes to avoid when solving 3 variable limit problems include forgetting to check for discontinuities or using incorrect substitution values. It is also important to double-check your algebraic manipulations and to use the correct limit laws and theorems.

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