@Christopher2222 

thank you. i think something was wrong with my worksheet. it is working now, so something must have been set in the variables.

@Axel Vogt thanks, shift+enter worked 

sample.mw

here is a sample worksheet. I created a new worksheet then pasted in the latest assignment.

@Markiyan Hirnyk 

this is great! thanks for posting

Thanks all for the variety of responses. I learned a lot from them.

I realize my error was one of inputting the function. What looked to me like cos(x) was in not as it appeared.

I have made similar input errors by assuming (x)(y) would be interpreted as (x)*(y).

So I'm learning when I need to be very careful with my input. It seems in this case, using the Expression Pallette is helpful when I'm unsure of syntax.

Thanks again for the replies

Brent

@Markiyan Hirnyk thank you, this is useful information. 

I agree with your earlier comment:

For completeness, it would be useful

to include the black square symbol in the Miscellaneous palette.

@Markiyan Hirnyk I understand your comment. Unfortunately, polygraphic workers do not grade my assignment, my professor does. I am required to use the black square symbol. I cannot find it in any palette. :(

@Carl Love 

that worked perfect, thank you :)