Hello,

I'm new using Mathematica. I'm trying to use Mathematica to follow a demostration where I have to perform transformations in expressions.

I arrive to the following problem: in a part of an expression, I need to use the following replacement: Sin(x) = -Sin(-x). So I apply it as follows:

F1 = 1 + Sin[a - b]

Replace[F1, Sin[x_] -> -Sin[-x]]

I was expecting the following result: F1=1-Sin[b-a]

However, I find Mathematica gives the initial result, that is: F1=1 + Sin[a - b]

I guess Mathematica tries to simplify the expression and arrives to the initial expression.How can I avoid this? I have tried several ways, but without success...

Thank you.