Mathcad Prime 5.0: Error in Summation Expression

For the future - please always attach the worksheet itself, not just a picture.

The ex-product (cross product x) is defined for vectors with three dimensions only.

The red encircled expression does not evaluate as such but is a 5-dimensional vector (because of u), while the second part is just a scalar.

What do you have in mind with a cross product of a five element vector with a scalar? What should that be?

What is it really you are looking for? Guess you did not meant to use a cross product, right?

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@saadhere wrote:

i am trying to write this expression in mathcad prime. (please see the attached pic)

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u in the picture is a function (obviously defined elsewhere), taking r as argument.

And the cross "x" seems to just denote a simple normal multiplication of scalars ("*").

What the picture shows is just basic numeric integration (trapezoid rule).

If you vector u holds the appropriate function values, you have to replace u(r[i) in the picture for u[i, etc. And the cross "x" is replaced  by a "*". Then it should work OK.