@acer 

@Rouben Rostamian

Thank you both for your insightful explanations and examples!

I also came across the command "Assume" from the "Physics" package. Unlike "assume", it does not redefine the variables receiving assumptions. The online documentation for "Assume" https://www.maplesoft.com/support/help/maple/view.aspx?path=Physics%2FAssume includes explanations and examples similar to yours.

It seems that another alternative is "assuming", which doesn't redefine the variables either. It only has effect on the command with which "assuming" is used.

Unfortunately, the fact that "assume" redefines the variables every time is nowhere mentioned in its documentation https://www.maplesoft.com/support/help/Maple/view.aspx?path=assume&cid=197 This is very unhelpful for any nonexpert who stumbles upon such issue.