Simplify cos(2 arcsec(2)).
simplify: cos( 2 · arcsec(2) )
Since sec = 1 / cos and cos = 1 / sec
arcsec( 2) = arccos( 1/2 ) = 60o
cos( 2 · arcsec(2) ) = cos( 2 · 60o ) = cos( 120o ) = .......