Finding the Limit of Trig Functions: 2x/sin3x, x->0

In summary, the problem involves finding the limit of 2x/sin3x as x approaches 0. Using the known limit of sinx/x as x approaches 0, the solution attempts to rewrite the problem as 2/3 (3x)/sin(3x) in order to solve. However, it is noted that this is not the same as (2/3)sin(x)/x and therefore, the solution is not correct. The correct approach would be to use the known limit of cos2x(2)/3 as x approaches 0.
  • #1
domyy
196
0

Homework Statement



lim 2x/(sin3x)
x-> 0

Homework Equations



lim sinx/x = 1
x->0

The Attempt at a Solution



is it correct to say the following:

lim 2/3 (sinx/x)
x-> 0

lim 2/3 (1)
x-> 0

Answer: lim 2x/sin3x = 2/3
x-> 0

Because it's on the book:
cos 2x(2)/3 = 2/3
x->0

So I want to know if I solve it the way I did before, would it be correct?
 
Last edited:
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  • #2
domyy said:

Homework Statement



lim 2x/(sin3x)
x-> 0


Homework Equations



lim sinx/x = 1
x->0

The Attempt at a Solution



is it correct to say the following:

lim 2/3 (sinx/x)
x-> 0

lim 2/3 (1)
x-> 0

Answer: lim 2x/sin3x = 2/3
x-> 0

Because it's on the book:
cos 2x(2)/3 = 2/3
x->0

So I want to know if I solve it the way I did before, would it be correct?

lim 2/3 sin(x)/x is zero at x=0, but 2x/sin(3x) is not the same as (2/3)sin(x)/x.

Rewrite 2x/sin(3x) as 2/3 (3x)/sin(3x).

ehild
 
  • #3
Thanks! Got it! =)
 

Related to Finding the Limit of Trig Functions: 2x/sin3x, x->0

1. What is a limit of a trigonometric function?

A limit of a trigonometric function is the value that a function approaches as its input (x-value) approaches a specific value. It is denoted by the notation "lim f(x) as x approaches a".

2. How is the limit of a trigonometric function calculated?

The limit of a trigonometric function can be calculated using algebraic techniques, such as factoring or simplifying. It can also be calculated using the rules of limits, such as the sum, product, and quotient rules.

3. What are the common trigonometric functions?

The common trigonometric functions are sine (sin), cosine (cos), tangent (tan), cotangent (cot), secant (sec), and cosecant (csc). These functions relate the angles of a triangle to the lengths of its sides.

4. Can the limit of a trigonometric function be undefined?

Yes, the limit of a trigonometric function can be undefined if the function has a vertical asymptote or if the function oscillates infinitely as x approaches a certain value.

5. Why are limits of trigonometric functions important?

Limits of trigonometric functions are important because they allow us to understand the behavior of these functions at certain points and to make predictions about their values. They also play a crucial role in calculus and other areas of mathematics.

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