Here's a grouping for you 4x. You can write it as (4x) or (4)(x), or 4*x. It doesn't much matter, they all represent multiplication. Juxtaposed implicit multiplication is just multiplication plain and simple. 1/2π is half of the value of pi. Pi being 3.14...... half of that is 1.57.... It is definitely not 1 / (2π) despite what you believe!