Hi, got a problem defining variables in cloud.sagemath: http://www.directupload.net/file/d/3699/bs9eya98_png.htm
I just copied the code from http://www.sagemath.org/doc/reference/calculus/sage/calculus/calculus.html (the very first line) but I also tried it myself with different letters and '`ยด". None worked.
