Question 1062437
{{{ 5*pi/4 = 4*pi/4 + pi/4 }}}
{{{ 5*pi/4 = pi + pi/4 }}}
This is a CCW turn of the radial vector {{{ pi/4 }}}
radians past the {{{ pi }}} radian vector,
putting the angle in the 3rd quadrant
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The negative co-terminal angle is
a CW turn of the radial vector by
{{{ -pi/2 - pi/4 = -3*pi/4 }}}, the same position in the 3rd quadrant
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{{{ pi/4 }}} radians = {{{ 45 }}} degrees
{{{ 5*pi/4 }}} radians = {{{ 5*45 }}} degrees
{{{ 5*45 = 225 }}} degrees
( also {{{ -3*pi/4 }}} radians = {{{ -135 }}} degrees 
is the negative co-terminal angle )