Finding the limit of trignometric functions

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Homework Help Overview

The discussion revolves around finding the limit of the expression (h sin h) / (1 - cos h) as h approaches 0, which falls under the subject area of limits in calculus, specifically involving trigonometric functions.

Discussion Character

  • Exploratory, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • Participants discuss manipulating the limit expression and consider breaking it into parts. Questions arise about the relationship between the limits of sin h / h and h / sin h, as well as the implications of known limit values.

Discussion Status

Some participants express agreement on the limit's value being 2, while others clarify the understanding of the limits involved. There is an acknowledgment of the approach being somewhat indirect, and one participant indicates a lack of familiarity with L'Hopital's Rule, suggesting that the current method is the only one they can use.

Contextual Notes

One participant notes that they have not yet learned L'Hopital's Rule, which may influence the methods available for solving the problem.

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Homework Statement



Find the Limit: lim h->0 of ( h sin h)/ ( 1-cos h)

Homework Equations



lim h->0 of (sin theta)/ theta = 1
lim h->0 of (cos(h)-1)/h=0

The Attempt at a Solution


lim h->0 (h/1-cos h)*(sin h) * (1+cos h/ 1 +cos h)

= lim h->0 (h(1+cos h) * sin h)/(1-cos^2 h)

= lim h->0 (h(1+cos h))/sin h

That's how far I got, I have no idea how to continue.
Please and thank you!

 
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panadaeyes said:

Homework Statement



Find the Limit: lim h->0 of ( h sin h)/ ( 1-cos h)

Homework Equations



lim h->0 of (sin theta)/ theta = 1
lim h->0 of (cos(h)-1)/h=0

The Attempt at a Solution


lim h->0 (h/1-cos h)*(sin h) * (1+cos h/ 1 +cos h)

= lim h->0 (h(1+cos h) * sin h)/(1-cos^2 h)

= lim h->0 (h(1+cos h))/sin h

That's how far I got, I have no idea how to continue.
Please and thank you!
You're almost there!
[tex]=\lim_{h \to 0} \frac{h}{sin(h)}\cdot (1 + cos(h))[/tex]

You can break up the limit of a product to the product of limits, provided that both limits exist. Hint: look at your relevant equations.
 
Mark44 said:
You're almost there!
[tex]=\lim_{h \to 0} \frac{h}{sin(h)}\cdot (1 + cos(h))[/tex]

You can break up the limit of a product to the product of limits, provided that both limits exist. Hint: look at your relevant equations.

Okay, so I split them up, but would the equation: lim h->0 of sin h/ h = 1 be the same as the lim h->0 of h/sin h?? how does that work?

and therefore be: 1 * lim h->0 (1+ cos h)
= 1 * 2 = 2?
 
Yup, I get 2 also.

If you know limh→0 h/sinh = 1 then you know that
limh→0 (sinh/h)-1 = 1.

But (sinh/h)-1 = 1 ⇒ (sinh/h)= 1


Edit: You don’t know l’hopital’s rule right? If you do this is a rather round-about way to do this problem.
 
Last edited:
JonF said:
Yup, I get 2 also.
Agreed.
JonF said:
If you know limh→0 h/sinh = 1 then you know that
limh→0 (sinh/h)-1 = 1.

But (sinh/h)-1 = 1 ⇒ (sinh/h)= 1
Not sure what the missing symbol is - implies?
But sinh/h [itex]\neq[/itex] 1. The limit as h -> 0 is 1, though.
JonF said:
Edit: You don’t know l’hopital’s rule right? If you do this is a rather round-about way to do this problem.
But if the OP doesn't know L'Hopital's Rule, this is the way to go.
 
Yah, I haven't learned L'Hopital's Rule yet

But thanks guys!
 

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