tan675°+cos765°-tan(300°)+cos(-690°)
=tan(675-540)°+cos(765-720)°+tan(360-300)°+cos(720-690)°
=tan135°+cos45°+tan60°+cos30°
=-1+根号2/2+根号3+1/2
=根号3+根号2/2-1/2
tan675°+cos765°-tan(300°)+cos(-690°)
=tan(675-540)°+cos(765-720)°+tan(360-300)°+cos(720-690)°
=tan135°+cos45°+tan60°+cos30°
=-1+根号2/2+根号3+1/2
=根号3+根号2/2-1/2