# Simple equation

1. May 4, 2006

### dervast

Hi i need a little help with an equation

Ber=1/2*exp(-rT)
I want to solve it to -rT
Which of the following solutions is correct?
ln(BER/2)=-rT or
ln(BER/2)=rT

2. May 4, 2006

### J77

Neither...

First, exp(-rT)=2*Ber

I think you can do the rest and remember to show respect to that minus sign

3. May 4, 2006

### dervast

No i dont remember how to do it :(
What i know it that
exp(x)=theta
ln(theta)=x

4. May 4, 2006

### J77

$$2B=e^{-rT}\implies ln(2B)=-rT$$

If you want to go further...

$$aln(x)=ln(x^a)$$ can be used

5. Jan 26, 2008

### ekhlas

iam ph.d studentin electrical enginerring/USM/MALYSIA
Ihave some equestion
1-my research :new noise measurement techniques sing it error rate,iwant ask how make the relation ship betwen BER,NF LINERITY
2-CAN HELP ME FOR FIND NEW EQUATION OF BER RELATED TO NF
THANK U VERY MUCH FOR HELP ME