Question 939306
{{{sin(-7*pi/2) =  sin(-7*90) }}}   as {{{ pi/2  = 90}}} degrees
                ={{{  sin (-630)}}}
                = {{{-sin(630)}}}   as {{{sin ( -theta ) =-sin(theta)}}}
                 ={{{-sin(720-90)}}}
             ={{{- sin (90)}}}
                ={{{-1}}}               as sin 90  = 1
             = -1
 Result : Sin (-7pi/2) = -1