Trying to isolate a variable and keep getting stuck

[Dari]

I have an equation: exp(-a)*exp(-b) +c = exp(-d)

I'm trying to isolate a variable but I'm not sure what to do with the left side when I take the natural log of both sides. that c is bothering me me. Any ideas?

 

[chuckywang]

Originally posted by: Dari
I have an equation: exp(-a)*exp(-b) +c = exp(-d)

I'm trying to isolate a variable but I'm not sure what to do with the left side when I take the natural log of both sides. that c is bothering me me. Any ideas?

What variable are you trying to isolate?

The natural log of sums is just that ... the natural log of sums. You can't simplify it down any more.

 

[Dari]

Originally posted by: chuckywang

Originally posted by: Dari
I have an equation: exp(-a)*exp(-b) +c = exp(-d)

I'm trying to isolate a variable but I'm not sure what to do with the left side when I take the natural log of both sides. that c is bothering me me. Any ideas?

What variable are you trying to isolate?

The natural log of sums is just that ... the natural log of sums. You can't simplify it down any more.

the variable is in a,b and d. are you saying that I cannot simply: ln(exp(-a)*exp(-b) +c) = ln(exp(-d)) any further?

 

[apepooooop]

what are a, b, and d

 

[Dari]

Originally posted by: apepooooop
what are a, b, and d

0.7, 3.3*X, and 0.25+3.75*X, respectfully. a and c are constants.

 

[TuxDave]

Have you used these identities?

exp(a)*exp(b) = exp(a+b)
exp(a)/exp(b) = exp(a-b)

With that you should be able to rearrange the equation into:

exp(k*x) = blah

And then you can do the natural log and solve.

 

[Dari]

Originally posted by: TuxDave
Have you used these identities?

exp(a)*exp(b) = exp(a+b)
exp(a)/exp(b) = exp(a-b)

With that you should be able to rearrange the equation into:

exp(k*x) = blah

And then you can do the natural log and solve.

yeah, I've done all that. Anyone know how to solve a single equation in matlab?

 

[Dari]

nevermind, I just used the fzero funtion.