Question

what is the value of cos(npi/2)

Answer 1

I don't know.
Check these.
http://answers.yahoo.com/question/index?qid=20070314101632AABfxtA
http://math.stackexchange.com/questions/53202/how-do-you-solve-this-series-question-cos-n-pi-ln6n

Answer 2

@harsid Those links don't really relate to the asked problem.

Anyway, assuming that \(\bf n\) is an integer, we have the following:\[\bf \cos \left( \frac{ n \pi}{ 2 } \right)=0 \ | \ n=\frac{ \pi }{ 2 }+2 \pi k \ \ or \ \ n=\frac{ 3 \pi }{ 2 }+2 \pi k, \ k \in \mathbb{Z}\]

Answer 3

You could also say that the values lies within 1 and -1 for real numbers 'n'...