如图,点E在直线DF上,点B在直线AC上,若∠AGB=∠EHF,∠C=∠D.
求证:∠A=∠F.
证明:∵∠AGB=∠EHF
∠AGB=____(对顶角相等)
∴∠EHF=∠DGF
∴DB∥EC(____)
∴∠____=∠DBA(____)
又∵∠C=∠D
∴∠DBA=∠D
∴DF∥____(____)
∴∠A=∠F(____).
在国际单位制中,质量的基本单位是 ____ ,航天员将地球上质量为50kg的物体带到月球上,此时物体的质量将 ____.(选填“变大”,“不变”,或“不变”)
The students stopped ____ (talk) when the teacher came in.