Trig Limit Homework Help: Solving (2sinxcosx)/ (2x^2 + x) at x=0

In summary, the limit of (2sinxcosx)/(2x^2+x) as x approaches 0 is equal to 2. This can be found by rewriting the expression as sin(2x)/(2x(x+1/2)) and then taking the limit of sin(2x)/2x, which is equal to 1, and multiplying it by 1/(x+1/2). Alternatively, the limit can be found directly by factoring the denominator and simplifying the expression.
  • #1
jog511
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Homework Statement



lim x->0 (2sinxcosx)/ (2x^2 + x )

Homework Equations


2sinxcosx = sin(2x)


The Attempt at a Solution


denom. factors to x(2x +1) how to proceed?
 
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  • #2
jog511 said:

Homework Statement



lim x->0 (2sinxcosx)/ (2x^2 + x )

Homework Equations


2sinxcosx = sin(2x)


The Attempt at a Solution


denom. factors to x(2x +1) how to proceed?

Your expression can be rewritten as ##\frac{\sin(2x)}{2x(x + 1/2)}##. Does that help?
 
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  • #3
the limit of sin2x/2x will be 2. am I on the right track?
 
  • #4
sin2x/2x will be 1 I mean
 
  • #5
can it be written as sin2x/2x * 1/(x + 1/2)
 
  • #6
jog511 said:
can it be written as sin2x/2x * 1/(x + 1/2)

Yes, that's the idea.
 
  • #7
I get lim = 2
 
  • #8
very helpful
 
  • #9
jog511 said:
I get lim = 2

Yes, but note that you could actually have done it directly:

[tex]\lim_{x→0}\frac{2sin(x)cos(x)}{2x^2+x}= 2\lim_{x→0}\frac{sin(x)}{x}cos(x)\frac{1}{2x+1}=2[/tex]
 
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FAQ: Trig Limit Homework Help: Solving (2sinxcosx)/ (2x^2 + x) at x=0

What is a trig limit?

A trigonometric limit is a mathematical concept that represents the value that a function approaches as the input variable approaches a specific value. In other words, it is the value that the function "gets close to" but never actually reaches.

Why is finding a trig limit important?

Trigonometric limits are important in calculus because they help us understand the behavior of functions near specific points. They also allow us to evaluate complicated functions that cannot be solved directly.

How do I solve a trig limit?

Solving a trigonometric limit involves using various algebraic and trigonometric identities and techniques, such as factoring, rationalizing, and using the properties of limits. In some cases, a graphing calculator may also be helpful.

What are some common types of trig limits?

Some common types of trigonometric limits include limits involving sine, cosine, tangent, secant, and cotangent functions. These limits may involve various trigonometric identities, limits at infinity, or special angles.

Can I use L'Hopital's rule to solve a trig limit?

Yes, L'Hopital's rule can be used to solve certain types of trigonometric limits. This rule states that if the limit of a function f(x)/g(x) as x approaches a specific value is an indeterminate form (such as 0/0 or ∞/∞), then the limit of the derivative of f(x) divided by the derivative of g(x) is equivalent to the original limit. However, this rule should be used with caution and may not always yield an accurate result.

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