functions with parts  topic started 11/19/2001; 11:23:49 AM last post 11/20/2001; 12:19:30 PM 

Arnold K. Pizer  Re: functions with parts 11/20/2001; 12:19:30 PM (reads: 912, responses: 0) 
In version 1.7 there is a step(x) function which is 1 if x > 0 and 0 if x <= 0. So having the student enter x^2*step(x) + x*step(x) would give you your particular example above. Of course if you really need a function which is 1 if x >= 0 and 0 if x < 0, things become more complicated ( e.g. cos(x)*[1step(x)] ) and get more complicated still if the step or steps are off set from zero. For fairly simple cases, it is probably not too hard to show students how to use this step function. If we allowed functions of multiple variables [e.g. char(3,5,x) for the characteristic function on the interval (3,5)] and found a good way to denote what happens at the end points (e.g. char_oo, char_oc, char_co, char_cc where o means open and c closed), then having students use these functions would probably be reasonable and instructive. Such functions can be built from step(x), but not in a resonable manner. 