Răspuns :
Nu poate fi decat asa!
sin160+cos160 -a=
sin 160 =sin 20
cos 160 =-cos 20
sin160+cos160 -a= sin20 -cos20 -sin20 +cos20 =0
sin160+cos160 -a=
sin 160 =sin 20
cos 160 =-cos 20
sin160+cos160 -a= sin20 -cos20 -sin20 +cos20 =0