Question 316691
{{{pi}}} radians = 180 degrees
{{{pi/2}}} radians = 90 degrees
{{{(7*pi)/2}}} radians = 90 + 90 + 90 + 90  + 90 + 90 + 90 = 630 degrees
{{{630/360}}} = 1 3/4
This is a complete turn from 0 degrees back to 0 degrees and
then a 3/4 turn
This is the same as -90 degrees
{{{sin(-90) = -1}}}