Limit of (arcsen(2x)-2arcsen(x))/x^3 as x->0

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In summary, the limit of (arcsen(2x)-2arcsen(x))/x^3 as x->0 is an 0/0 indeterminacy and can be solved using L'Hopital's rule. The process involves simplifying the expression by multiplying it by the conjugate root and using the derivative of the trigonometric function.
  • #1
tsuwal
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Homework Statement


Limit of (arcsen(2x)-2arcsen(x))/x^3 as x->0


Homework Equations


arsen(x)'=1/Sqrt(1-x^2)


The Attempt at a Solution


It's an 0/0 indeterminancy, to solve it, I had to use L'hopital's rule once simplify de expression, multiplying by the conjugate root. Is there an easier way?
 
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  • #2
As you don't get rid of the trigonometric functions without l'Hospital, I think this ok.

$$\frac{\frac{2}{\sqrt{1-(2x)^2}}-\frac{2}{\sqrt{1-(x)^2}}}{x^2} = 2 \frac{1}{\frac{1}{\sqrt{1-(2x)^2}}+\frac{1}{\sqrt{1-(x)^2}}} \frac{\frac{1}{1-(2x)^2}-\frac{1}{1-(x)^2}}{x^2} \to \frac{2}{2} \frac{\frac{1}{1-(2x)^2}-\frac{1}{1-(x)^2}}{x^2} \to \dots$$
 
  • #3
Thanks!
 

1. What is the definition of a limit in calculus?

The limit of a function is the value that a function approaches as the input approaches a certain value or approaches a point on the function. It is used to describe the behavior of a function at a specific point or as the input approaches a particular value.

2. What is the limit of a function as x approaches 0?

The limit of a function as x approaches 0 is the value that the function approaches as the input, x, gets closer and closer to 0. This can be found by evaluating the function at values of x that are very close to 0, either from the left or right side of 0.

3. How do you find the limit of a function algebraically?

To find the limit of a function algebraically, you can use various techniques such as factoring, simplifying, or using algebraic manipulations to rewrite the function. Then, you can substitute the given value for x and evaluate the function. If the resulting value is undefined, you may need to use L'Hopital's Rule or other methods to find the limit.

4. What is the limit of (arcsen(2x)-2arcsen(x))/x^3 as x approaches 0?

The limit of (arcsen(2x)-2arcsen(x))/x^3 as x approaches 0 is 1/6. This can be found by using algebraic manipulations and the limit definition of the derivative. Alternatively, you can use the power series expansion of arcsen(x) to evaluate the limit.

5. Why is the limit of (arcsen(2x)-2arcsen(x))/x^3 as x approaches 0 important?

The limit of (arcsen(2x)-2arcsen(x))/x^3 as x approaches 0 is important because it helps us understand the behavior of the function near the point where x=0. This limit can also be used to find the derivative of the function at x=0, which is useful in many applications of calculus.

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