# Limits problem

1. Sep 2, 2010

### Misr

1. The problem statement, all variables and given/known data

[PLAIN]http://img137.imageshack.us/img137/4242/probhr.jpg [Broken]

Well ,my problem is why after substitution for the first time the result os uncertainity (0/0)

Is X=0?

and I don't understand the step no 2

Last edited by a moderator: May 4, 2017
2. Sep 2, 2010

### vela

Staff Emeritus
What you've written doesn't make sense.

3. Sep 2, 2010

so.....?

4. Sep 2, 2010

### Dick

I think they mean the symbol you are writing as 'A' to be the symbol for pi.

5. Sep 2, 2010

### vela

Staff Emeritus
Go back and check that you accurately copied the original problem and the solution. It's pointless to try explain something that is wrong to begin with.

6. Sep 2, 2010

### Misr

awww you are right.The problem was written in another language so I translated it in a wrong way...I'll try to solve it again

Thanks for all of you

7. Sep 3, 2010

### Misr

Ok..I'm back
so I know that sin(180-x)=sin(pi-x)

but x= pi right?
so sin(pi-x) = sin (x-pi) ?
why did we use sin(pi-x) instead ?
hope u could understand me
thanks

8. Sep 3, 2010

### Dick

x doesn't equal pi. But for any x, sin(x)=sin(pi-x)=(-sin(x-pi)). Look at graph of the sin function or use a sin addition formula to prove that. They are using those identities to prove the limit.

9. Sep 3, 2010

### Misr

so why not?
isn't x-pi=0 as mentioned in the problem ?

10. Sep 3, 2010

### Dick

x-pi->0. That means x approaches pi (gets closer and closer to pi). It's not equal to pi. If x=pi then you have a zero in the denominator and the ratio is undefined.

11. Sep 3, 2010

### Misr

oh ok thanks very much