— What does your mother do, Li Jie?
— She is a (an) . She teaches (教书) in a high school.
A:office worker
B:doctor
C:nurse
D:teacher
我们知道:光反射时,反射光线、入射光线和法线在同一平面内,反射光线、入射光线分别在法线两侧,反射角等于入射角.如右图,AO为入射光线,入射点为O,ON为法线(过入射点O且垂直于镜面的直线),OB为反射光线,此时反射角∠BON等于入射角∠AON.
问题思考:
213 =____÷____ 1415 =____÷____
913 =____÷____ 415 =____÷____