西经74看成东经-74.
=r*arccos(sin(116)*sin(-74)+cos(116)*cos(-74)*cos(40-40))
=r*arccos(sin(116)*sin(-74)+cos(116)*cos(-74) )
=r*arccos(cos(116-(-74) ) )
=r*arccos(cos180 )
=π·
西经74看成东经-74.
=r*arccos(sin(116)*sin(-74)+cos(116)*cos(-74)*cos(40-40))
=r*arccos(sin(116)*sin(-74)+cos(116)*cos(-74) )
=r*arccos(cos(116-(-74) ) )
=r*arccos(cos180 )
=π·