Limit of sin4x/3x as x approaches 0: Squeeze Theorem

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In summary, the conversation is discussing finding the limit as x approaches 0 of sin(4x)/3x. The speaker attempted to manipulate the equation and questioned how sin(4x)/4x becomes 1. The other speaker points out that it is a known limit and suggests using the substitution u=4x. They also mention that it is likely the problem was given with the assumption that the limit u->0 of sin(u)/u=1 has already been proven.
  • #1
appplejack
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Homework Statement


Find lim sin4x/3x
x -> 0


Homework Equations





The Attempt at a Solution


I did some algebraic massaging and got

sin4/3x = 4/4 * sin4x/3x = 4/3 * sin4x/4x
but I don't understand how sin4x/4x becomes 1 like my textbook says so.
 
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  • #2
sin(4x)/(4x) isn't 1. The limit as x->0 of sin(4x)/(4x) is 1. Have you proved limit u->0 of sin(u)/u=1? Then just put 4x=u.
 
Last edited:
  • #3
Dick said:
sin(4x)/(4x) isn't 1. The limit as x->0 of sin(4x)/(4x) is 1. Have you proved limit u->0 of sin(u)/u=1? Then just put 4x=u.

Yeah you're right.So, It's true that limit u->0 of sin(u)/u=1?
 
  • #4
Didn't you prove limit u->0 sin(u)/u=1. I doubt they would have given you this problem if they hadn't.
 

What is the Squeeze Theorem?

The Squeeze Theorem, also known as the Sandwich Theorem or the Pinching Theorem, is a mathematical theorem used to prove the limit of a function by "squeezing" it between two other functions with known limits. It is commonly used to evaluate limits involving trigonometric, exponential, and logarithmic functions.

How do you use the Squeeze Theorem to evaluate a limit?

To use the Squeeze Theorem, you must have a function that is sandwiched between two other functions with known limits. If the two surrounding functions have the same limit as each other, then the middle function must also have the same limit.

Can the Squeeze Theorem be used to find the limit of any function?

No, the Squeeze Theorem can only be used when the function is squeezed between two other functions with known limits. Additionally, the two surrounding functions must have the same limit for the theorem to be applicable.

What are the common applications of the Squeeze Theorem?

The Squeeze Theorem is commonly used in calculus to evaluate limits involving trigonometric, exponential, and logarithmic functions. It is also used in real-world applications such as physics, engineering, and economics to model and analyze various systems.

Are there any limitations to the Squeeze Theorem?

Yes, the Squeeze Theorem can only be used to evaluate limits as x approaches a specific value. It cannot be used to evaluate limits at infinity or for limits that do not exist. Additionally, the theorem does not apply to functions that are not sandwiched between two other functions with known limits.

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