Question 1139953
180 degrees is 1/2 of a full rotation from
0 degrees. The {{{ sin(180) }}} = vertical/ unit vector
= {{{ 0/1 }}} which is zero
---------------------------------------
The sine is negative in the 3rd and 4th quadrants
{{{ arcsin( -.891 ) = 63 }}} degrees
{{{ theta = 180 + 63 }}}
{{{ theta = 243 }}}
and
{{{ theta = 360 - 63 }}}
{{{ theta = 297 }}} 
check the math