# Help finding a limit

1. May 19, 2008

### fishingspree2

1. The problem statement, all variables and given/known data
$$\mathop {\lim }\limits_{x \to 0} (1 - \cos x)$$

2. The attempt at a solution

well as x goes to 0, cos x goes to 1... ln(1-1) is undefined
now if I forget about plugging in x=0 and think a little bit, the ln argument gets very very small, and the logarithm of a decimal number is a negative number... so I would say the limit is minus infinity.

however, is it possible to get that result analytically.... by transforming/simplyfing/etc. the function?

sorry, I have just finished precalculus and I am beginning calculus, so my calculus skills are crap =\

thank you

Last edited: May 19, 2008
2. May 19, 2008

### rocomath

hmm ... problem is: $$\lim_{x\rightarrow0}(1-\cos x)$$?

Can't you just plug it in?

Or is it:

$$\lim_{x\rightarrow0}\ln{(1-\cos x)}$$

Ok so have the graph infront of you. You know as you "approach" coming from the right, it's negative infinity ...

$$\lim_{x\rightarrow0^{+}}\ln{(1-\cos x)}=-\infty$$

What about from the left? Because in order for the Limit to exist, the L & R Limits must agree. But for the natural logarithm, how is it uniquely defined?

Last edited: May 19, 2008
3. May 20, 2008

### kt9aq

Once you have learned L^Hopitals rule, you will be able to apply it to this equation and get the same answer analytically.