[Maxima] changevar problem with sin(x)+cos(x)=t

[Raymond Toy (RT/EUS)]

Robert Marik wrote:
> Dear members of maxima list
> 
> Maxima cannot change variables in the following integral
> 
> changevar('integrate(
> (sin(x)+cos(x))/sqrt(sin(x)-cos(x)),x
> ),sin(x)-cos(x)=t,t,x);

Maxima can already evaluate the integral.  Any particular reason why you 
want to use this substitution to do it?

> 
> the problem is probably caused by the fact that maxima cannot solve
> sin(x)+cos(x)=t with respect to t
> 
> Is there any workaround for this? Is there any way how to transform the
> integral of f'(x)g(f(x)) into g(t)  ?
> here f' denotes derivative.

I think maxima already knows how to do this, but I'm not 100% sure.

Ray