Range variable and trignometric Identity

Reason is that you are using a range variable for something its not made for.

But you are not the first to confuse ranges with vectors - unfortunately, it is a matter that constantly causes misunderstandings and confusion.

Ranges are kind of implicit loops, not a data structure which holds a couple of values (like a vector).

Ranges should only be used for

1) plots as the variable placed at the abscissa axis

2) indexing vectors and matrices

3) loops in a program

For your purpose you should define variable "k" as a vector, not a range.

Simply replace the definition   k:=0,0.2..1   by    k:=vec(0,0.2,1)   and all will work as you expected.

"vec" is a new function in Prime 11 and can be used to either define a vector (as just shown) or to convert a range into a vector. See the help for more information.