Evaluate each of the following limits. Show all reasoning.

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In summary, the conversation discusses how to find the limit of (2 tan^2 x)/x^2 as x approaches 0. The participants suggest rewriting tan x as sin x/cos x and using l'Hopital's rule or the known limit of sin x/x to simplify the expression. One participant confirms that the final answer is 2.
  • #1
ugeous
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lim (2 tan^2 x)/x^2
x->0

I am just uncertain about how to do this question. Do I find a derivative or something else? Just need some guidance.

Thanx.
 
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  • #2
If it were me, I would rewrite tan x as sin x/cos x and try to break the expression into parts.
 
  • #3
Remind me please, do you rewrite tan as sin/cos before taking derivative or after? I think it is before, but not 100% sure. Thanks
 
  • #4
Halls is guessing you know the limit x->0 of sin(x)/x. If so just substitute it. Otherwise, use l'Hopital.
 
  • #5
ugeous said:
Remind me please, do you rewrite tan as sin/cos before taking derivative or after? I think it is before, but not 100% sure. Thanks
Why in the world would you take any derivative?
 
  • #6
Ooooh... I have thought of a completely different thing here. I understand it now.

thanks guys!
 
  • #7
just wanted to confirm with you guys (finding this topic a little difficult)

by converting tan^2x i get

lim 2sin^2x
x->0 cos^2x(x^2)

limit x->0 of sin^2x/x^2 gives 1 correct? then I am simply left with 2/cos^2x which gives me final answer 2. Am I correct? Thanks for help/comments.
 
  • #8
Yes, that's it.
 

1. What is a limit?

A limit is a mathematical concept that describes the behavior of a function as its input approaches a certain value. It is represented as the value that the function approaches, or the value it gets closer and closer to, as the input gets closer and closer to the given value.

2. How do you evaluate a limit?

To evaluate a limit, you must first plug in the given value into the function and see if it gives a meaningful result. If it does not, you may have an indeterminate form and will need to use other techniques such as factoring, rationalizing, or L'Hopital's rule to solve the limit. Otherwise, you can simply substitute the value and evaluate the function to find the limit.

3. What are the different types of limits?

There are several types of limits, including one-sided limits, infinite limits, and limits at infinity. One-sided limits only consider the behavior of the function from one side of the given value, while infinite limits describe the behavior of a function as it approaches infinity or negative infinity. Limits at infinity are limits where the input approaches infinity or negative infinity.

4. What are the common techniques for evaluating limits?

Some common techniques for evaluating limits include direct substitution, factoring, rationalizing, and using L'Hopital's rule. Other techniques include using trigonometric identities or using limits laws such as the sum, difference, product, and quotient laws.

5. How can you show reasoning when evaluating a limit?

To show reasoning when evaluating a limit, you can write out the steps you took to solve the limit, including any algebraic manipulations or other techniques used. You can also provide a graph or table to visually represent the behavior of the function as the input approaches the given value. Additionally, you can explain why certain techniques were used and how they help to solve the limit.

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