Question 934256
{{{ sec^2 ( 180 ) = 1 / cos^2 ( 180 ) }}}
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Use the fact that {{{ cos( 180 ) = -1 }}}
so, 
{{{ cos^2( 180 ) = (-1)^2 }}}
{{{ cos^2( 180 ) = 1 }}}
{{{ 1 / cos^2 ( 180 ) = 1/1 }}}
{{{ sec^2( 180 ) = 1 }}}