1. Because although you allocated zzi values for i from 100 to 1000, Mathcad automatically created a vector going from 0 to 1000. Because you didn't specify values for i going from 0 to 99 Mathcad set them to zero. Your attempted calculation then threw up a divide by zero error.
2. Better to supply the Mathcad worksheet than a pdf.
Ok...I changed i to 1..100 and it still doesn't work.
See attached.
That's because Mathcad starts counting at zero by default. You can change the origin if you want to. If you are only interested in i from 100 nto 1000 and then you could set ORIGIN:=100. (This is possible, but unusual! I often set ORIGIN:=1).
