Math Is Fun Forum

aznssj5gohan

Member

Registered: 2007-09-08

Posts: 1

Trig Limit

lim θ->0  (cosθ-1)/(sinθ)

Can i get some help on this question please

JaneFairfax

Member

Registered: 2007-02-23

Posts: 6,868

Re: Trig Limit

You can use L’Hòpital’s rule. The answer is 0.

aznssj5gohan

Member

Registered: 2007-09-08

Posts: 1

Re: Trig Limit

thanks. Can you give a example for L’Hòpital’s rule plz?

saudi_boy

Member

Registered: 2006-11-01

Posts: 41

Re: Trig Limit

Examples

1.

apply L’Hòpital’s rule.

2. note:Applying the rule a single time still results in an indeterminate form. In this case, the limit may be evaluated by applying l'Hôpital's rule three times:

Last edited by saudi_boy (2007-10-09 21:53:09)

Krizalid

Member

Registered: 2007-03-09

Posts: 51

Re: Trig Limit

Do we really need L'Hôpital's Rule?

What about if you multiply top & bottom by

?

JaneFairfax

Member

Registered: 2007-02-23

Posts: 6,868

Re: Trig Limit

Do we really need L'Hôpital's Rule?

What about if you multiply top & bottom by

?

Unless I’m missing something, it makes no difference.

Hunt

Member

Registered: 2007-09-29

Posts: 9

Re: Trig Limit

Multiplying by Sin(theta) works too.

JaneFairfax

Member

Registered: 2007-02-23

Posts: 6,868

Re: Trig Limit

I see, thanks. Although L’Hòpital works just as quickly so there’s nothing wrong with that method either.

Krizalid

Member

Registered: 2007-03-09

Posts: 51

Re: Trig Limit

Of course there's nothing wrong, it's more interesting to compute limits without him.