Question 732893
{{{ -7*pi/2 }}} is telling you to rotate around the unit circle 
{{{ 7 }}} times in the clockwise direction in increments of
{{{ pi/2 }}}.
You know that if you rotate by {{{ pi/2 }}} 4 times, you will come
back to where you started. That leaves {{{ 3*pi/2 }}} that you 
have to rotate in the clockwise direction.
The rotating arrow is now pointing in the positive vertical
direction. This is the same angle as {{{ pi/2 }}}, so
{{{ sin( pi/2 ) = 1 }}}
{{{ csc( pi/2 ) = 1 }}}
{{{ cos( pi/2 ) = 0 }}}
{{{ sec( pi/2 ) = infinity }}}
{{{ tan( pi/2 ) = infinity }}}
{{{ cot( pi/2 ) = 0 }}}