I have a big expression with multiple terms. The expression is kind of :

expr = a*ln(u) + b*ln(u) + a*ln(v)+b*ln(v)

I want to factor ln(u) and ln(v) to get (a+b)*ln(u) + (a+b)*ln(v)

I tried factor(expr,ln(u)) but I get the error :
Error, (in factor) 2nd argument, ln(2*da+(4*da^2+4*d^2-4*da*Sigma[a]+Sigma[a]^2+Delta[b]^2)^(1/2)-Sigma[a]), is not a valid algebraic extension.

I tried without Delta[b] and Sigma[a] : deltab and sigmaa but it didn't work either.

Do you have an idea how to factor the many ln ?

Thanks,
Mathieu

Hi,

I would like to format the solution given by maple.
I have the answer given by a paper and I would like to reproduce the same formula.

I have the expression :

(a1/2+a2/2)*ln(a1/2+a2/2+sqrt((a1/2+a2/2)^2+(b1/2-b2/2)^2+d^2))+(a1/2-a2/)*ln(a1/2-a2/2+sqrt((a1/2-a2/2)^2+(b1/2-b2/2)^2+d^2))

I would like to assume deltaa = a1-a2 and sigmaa = a1+a2.

The issue is that algsubs(deltaa = a1-a2, expr), my a1+a2 is replaced by deltaa+2*a2 and same for algsubs(sigmaa = a1+a2, expr), so i can't have sigmaa*ln(...) + deltaa*ln(...).

And all my squares are developed, for example I have : sqrt(1/4*a1^2+1/4*a2^2+1/2*a1*a2+...)

I can't put them in canonical form (1/2*a1+1/2*a2)^2 to get (1/2*sigmaa)^2.

Sorry for my english,
If you know how to do, i would be really grateful !

Mathieu