# How do you simplify # [cos(1/2)(phi)] x [cos(1/2)(phi)]#?

##### 1 Answer

Nov 14, 2016

Perhaps

(...but note the assumption that I made as to what was intended as the original expression)

#### Explanation:

If the expression was meant to be:

then since

we get the answer shown above.

...but maybe you meant

or something else... (???)