How to Solve Trigonometric Limits Using l'Hopital's Rule

In summary, the conversation discusses how to solve the limit \lim_{x\rightarrow0}\frac{x+sinx}{2x-sin3x} using techniques such as l'Hopital's rule and the limit of sin(x)/x. The final answer is found to be -2.
  • #1
mtayab1994
584
0

Homework Statement



solve the following limit: [tex]\lim_{x\rightarrow0}\frac{x+sinx}{2x-sin3x}[/tex]

The Attempt at a Solution



I know the principle of solving all sorts of limits but not trig limits, and since we just started trig limits it's still not clear to me, but i think to solve it we have to separate it then solve but i don't know. Any help on how to start please?
 
Physics news on Phys.org
  • #2
Do you know l'Hopital's rule?
 
  • #3
No haven't learned it can you fill me on it please?
 
  • #4
mtayab1994 said:

Homework Statement



solve the following limit: [tex]\lim_{x\rightarrow0}\frac{x+sinx}{2x-sin3x}[/tex]

The Attempt at a Solution



I know the principle of solving all sorts of limits but not trig limits, and since we just started trig limits it's still not clear to me, but i think to solve it we have to separate it then solve but i don't know. Any help on how to start please?
Are you familiar with Taylor series ?

Added in Edit:

Better yet:
multiply by (1/x) over (1/x) .​
 
  • #5
mtayab1994 said:
No haven't learned it can you fill me on it please?

You may not have covered it yet so you may be expected to do it a different way. Divide the numerator and denominator by x. Now you probably do know the limit sin(x)/x. Try to use that to find the limits of the terms.
 
  • #6
SammyS said:
Are you familiar with Taylor series ?

No sorry I'm not familiar with taylor series, but i know that for l'hospital's rule we have to take the derivative of the numerator and the derivative of the denominator; but i have never learned derivatives so i can't do that. Is it possible to solve it some other way?
 
  • #7
Ok the derivative of x+sinx is cosx+1 and how about the bottom?
 
  • #8
ok i counted and found the limit to be -2 is that correct?
 
  • #9
mtayab1994 said:
ok i counted and found the limit to be -2 is that correct?

Yes, if you used l'Hopital then you might check whether that is allowed. Otherwise you should try doing it using that the limit of sin(x)/x is 1.
 
  • #10
Dick said:
Yes, if you used l'Hopital then you might check whether that is allowed. Otherwise you should try doing it using that the limit of sin(x)/x is 1.

Yea thank you very much I get the trick. It's the same for almost all of them.
 

FAQ: How to Solve Trigonometric Limits Using l'Hopital's Rule

What is a trigonometric limit?

A trigonometric limit is a mathematical concept used to describe the behavior of a function as the input values approach a certain value. In other words, it is the value that a function approaches as the input values get closer and closer to a specific value.

How do you solve a trigonometric limit?

To solve a trigonometric limit, you must use a combination of algebraic manipulations and trigonometric identities to simplify the expression and then apply the limit laws to evaluate the limit.

What are some common trigonometric identities used to solve limits?

Some common trigonometric identities used to solve limits include the Pythagorean identities, sum and difference identities, and double angle identities.

What are the main steps in solving a trigonometric limit?

The main steps in solving a trigonometric limit include identifying the type of limit (finite or infinite), simplifying the expression using trigonometric identities, applying limit laws, and evaluating the limit.

Are there any special cases to consider when solving trigonometric limits?

Yes, there are a few special cases to consider when solving trigonometric limits, such as limits involving indeterminate forms (such as 0/0 or ∞/∞) and limits involving trigonometric functions with irrational or undefined values (such as sin(π/2) or tan(π)). In these cases, additional techniques such as L'Hôpital's rule or trigonometric substitutions may be necessary to solve the limit.

Similar threads

Replies
5
Views
803
Replies
7
Views
953
Replies
14
Views
1K
Replies
8
Views
1K
Replies
3
Views
2K
Replies
7
Views
1K
Replies
6
Views
2K
Back
Top