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Logs question, help plz?

 
 
cookiez
 
Reply Sat 23 Apr, 2005 05:10 pm
Hello, can anyone help me with rearranging this equation in terms of y? Confused

(1/2) ln ( y^2+1) = ln | 1+x | + ln A { A is an arbitrary constant }

AND

y + ln (y) = ln ( x- 1 ) + 1

Thanks in advance
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raprap
 
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Reply Sat 23 Apr, 2005 06:40 pm
Remember the laws of exponents
& I'm assumming that ln is a natural (rather than a common) logarithm/

(1/2) ln ( y^2+1) = ln | 1+x | + ln A
ln ( y^2+1)^(1/2) = ln | 1+x | + ln A
ln (( y^2+1)^(1/2)) - ln | 1+x | = ln A
ln ((( y^2+1)^(1/2)/(| 1+x |)=ln A
((( y^2+1)^(1/2)/(| 1+x |)=exp(ln A)=A
(( y^2+1)^(1/2)=A| 1+x |
y^2+1=(A|x+1|)^2
y^2= (A|x+1|)^2-1
y=sqrt[(A|x+1|)^2-1]

This one is easier to put into y in terms of x
y + ln (y) = ln ( x- 1 ) + 1
y-1+ln(y)=ln(x-1)
y-1=ln(x-1)-ln(y)
y-1=ln((x-1)/y)
ln((x-1)/y)=y-1
(x-1)/y=exp(y-1)
x-1=y*exp(y-1)
x=y*exp(y-1)+1

Rap
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cookiez
 
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Reply Sat 23 Apr, 2005 06:48 pm
thnx very much Rap Very Happy
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