Trigonometry Limits: Solving lim x -> 0 sin x / sin(x/2)

In summary, by using the double angle formula, we can rewrite the given limit as 2cos(x/2) which approaches 2 as x approaches 0. This confirms that the given limit is indeed equal to 2.
  • #1
Deathfish
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Homework Statement



Find lim x -> 0 [tex]\frac{sin x}{sin\frac{x}{2}}[/tex]

The Attempt at a Solution



Since period of sin 2(x/2) is T/2 compared to period T of sin (x/2)

sin 2(x/2) nears twice the value of sin (x/2) for all values of x approaching zero.

Therefore lim x -> 0 [tex]\frac{sin x}{sin\frac{x}{2}}[/tex] = 2

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somehow i find the reasoning flawed, anyone can offer a better solution?
 
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  • #2
Did you think to try L'Hospital's Rule?
 
  • #3
if you don't want to use Calculus (though this is in the Calculus section!), use the double angle formula, sin(2a)= 2 sin(a)cos(a) to write this as
[tex]\frac{2sin\left(\frac{x}{2}\right)cos\left(\frac{x}{2}\right)}{sin\left(\frac{x}{2}\right)}[/tex]
 

FAQ: Trigonometry Limits: Solving lim x -> 0 sin x / sin(x/2)

What is the definition of a limit in trigonometry?

A limit in trigonometry refers to the value that a function approaches as its input (x) approaches a specific value (a). It represents the behavior of the function at a certain point and is denoted by the notation lim x->a f(x).

How do you calculate limits in trigonometry?

To calculate a limit in trigonometry, you can use the algebraic method to simplify the expression or the trigonometric identities to rewrite the function. You can also use a graphing calculator or online limit calculator to find the limit.

What is the difference between a one-sided limit and a two-sided limit in trigonometry?

A one-sided limit only considers the behavior of a function as x approaches the specific value from one side (either the left or the right). A two-sided limit takes into account the behavior of the function from both sides of the specific value.

Can a limit in trigonometry be undefined?

Yes, a limit in trigonometry can be undefined. This usually occurs when the function has a vertical asymptote or a point of discontinuity at the specific value. In this case, the limit does not exist.

How are limits used in trigonometry in real-life applications?

Limits in trigonometry are used to model and analyze various real-life phenomena, such as the motion of objects, waves, and oscillations. They are also used in engineering, physics, and other fields to optimize designs and predict outcomes.

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