Solving Limit: Cos(xy) - 1 over x^2 y^2

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In summary, a limit is a mathematical concept used in calculus to describe the behavior of a function as its input approaches a certain value. To solve limits, techniques such as direct substitution, factoring, and L'Hopital's rule can be used. Algebraic manipulation can also be helpful in simplifying expressions. The purpose of finding limits is to analyze the behavior of functions and make predictions in various fields. When solving the limit of cos(xy) - 1 over x^2 y^2, the expression can be simplified and the individual limits can be evaluated. In this case, the limit is undefined.
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Kuma
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Homework Statement




question asks:

lim(x,y) -> (0,0)

cos(xy) -1 / [x^2 y^2]


Homework Equations





The Attempt at a Solution



if you multiply the top and bottom by cos(xy) + 1 you get

-[sin^2(xy)/(xy)^2] * [1/cos(xy) + 1]

but in the solution they somehow got rid of the denominator (xy)^2, because if that's there the denominator is still 0. How do you get rid of that?
 
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  • #2
The limit u->0 sin(u)/u=1. So limit u->0 sin(u)^2/u^2=1. That's what they did with the first term.
 

1. What is a limit?

A limit is a concept in calculus that describes the behavior of a function as its input approaches a certain value. It helps us understand the behavior of a function without actually evaluating it at that specific value.

2. How do you solve limits?

To solve a limit, you can use various techniques such as direct substitution, factoring, rationalization, and L'Hopital's rule. You can also use a graphing calculator or numerical methods to approximate the limit.

3. Can you use algebra to solve limits?

Yes, algebraic manipulation is often used to simplify expressions and make it easier to evaluate limits. For example, in the given expression, we can factor out a common factor of 1/x^2y^2 to simplify the expression before taking the limit.

4. What is the purpose of finding limits?

Limits are used in many areas of mathematics, physics, and engineering to analyze the behavior of functions and make predictions. They also play a crucial role in understanding derivatives and integrals, which are fundamental concepts in calculus.

5. How do you solve the limit of cos(xy) - 1 over x^2 y^2?

To solve this limit, we can first simplify the expression by factoring out a common factor of 1/x^2y^2. This yields the expression (cos(xy) - 1) / (x^2y^2). Then, we can use the fact that the limit of a quotient is equal to the quotient of the limits and evaluate the limit of each term separately. The limit of cos(xy) as x and y approach 0 is 1, and the limit of 1/x^2y^2 is 0. Thus, the overall limit is 1/0, which is undefined.

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