nSolve

[Han]

It appears I was a bit presumptuous -- I thought you were trying to use this command from the Home view (this is where single or double quotes would be necessary).

From home view, I typed: nSolve("cos(x)=x","x=1.3") and it works fine.
From CAS view, I typed: nSolve(cos(x)=x,x=1.3) and this work as well.

You are saying that in CAS view, typing nSolve(cos(x)=x,x=1.3) produces an error? Perhaps you have x already defined? To test, type x all by itself (lowercase) and see if it returns a real number (as opposed to just the variable itself). If so, then use purge(x) to delete the CAS variable. Most commands will balk at the use of a variable that has also been defined.

To add more complexity to the situation, storing a value into x in the Home view creates an x variable distinct from one created in the CAS view!