TR ¯»œNG THCS QUANG TRUNG

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TR ƯỜNG THCS QUANG TRUNG. HÌNH HOÏC 9. GV: NG Ô MINH LAN. Baøi : TÖÙ GIAÙC NOÄI TIEÁP. Câu 1:. Kiểm tra bài cũ:. Khi naøo tam giaùc ñöôïc goïi laø noäi tieáp trong moät ñöôøng troøn?. - PowerPoint PPT Presentation

Text of TR ¯»œNG THCS QUANG TRUNG

  • TRNG THCS QUANG TRUNG GV: NG MINH LAN

  • Kim tra bi c:

    Khi nao tam giac c goi lanoi tiep trong mot ng tron? Tam giac c goi la noi tiep ng tron khi ba nh cua tam giac nam tren ng tron o Cu 1:

  • Kim tra bi c:

    Tam cua ng tron ngoai tiep tam giac la giao iem ba ng nao trongtam giac ?Tam cua ng tron ngoai tiep tam giac la giao iem cua ba ng trung trc cua tam giac Cu 2:

  • AT VAN ETa a biet : Ba ng trung trc trong tam giac luon i qua mot iem . Tc la , ta luon ve c mot ng tron i qua cac nh cua mot tam giac. Phai chang ta cung lam c nh vay oi vi mot t giac ? Co phai bat k t giac nao cung noi tiep c ng tron ?

  • Bai 7 : T GIAC NOI TIEP1. Khai niem t giac noi tiep

  • ?1Ve mot ng tron tam O roi ve mot t giac co tat ca cac nh nam tren ng tron o .Ve mot ng tron tam I roi ve mot t giac co ba nh nam tren ng tron o

  • CU HIKhi nao mot t giac c goi la t giac noi tiep ?

  • 1.Khai niem t giac noi tiep : Mot t giac co bon nh nam tren mot ng tron c goi la t giac noi tiep ng tron ( goi tat la t giac noi tiep )Bai 7:T GIAC NOI TIEP nh ngha:OABCD

  • CAU HOI :Quan sat cac hnh ve sau , cho biet t giac nao la t giac noi tiep? ABCDOIMNEFMPQRSAKEMGHnh 1a)b)c)d)

  • Bai toan: Cho t giac ABCD noi tiep trong ng tron ( O ) .Chng minh :a) b)HOAT ONG NHOMGIAIGT KLT giacABCD noi tiep(O) OACOABCD

  • ss (nh l ve goc noi tiep )ssss( A, B, C,D cung nam tren ( O) ) OABCD?2

  • Ta co : T giac ABCD noi tiep ng tron tam ( O ) s(nh l goc noi tiep) (nh l goc noi tiep) : sMa:Suy ra: s (Ma : sssNen :Chng minh tng t : ABCDMa : sss(nh l goc noi tiep) Chng minh:

  • CAU HOI Qua bai toan tren , em co nhan xet g ve tong so o hai goc oi dien cua mot t giac noi tiep ?

  • 1.Khai niem t giac noi tiep :2. nh l : Trong mot t giac noi tiep , tong so o hai goc oi dien bang T giac ABCD noi tiep(O) ABCODBai 7:T GIAC NOI TIEP

  • Biet ABCD la t giac noi tiep . Hay ien o trong vao bang sau ( neu co the )TRNG HPGOC123456CUNG CO : Bai 53 trang 89 SGK

  • ABCDOIMNEFMPQRSAKEMGHnh 1Hay xem lai hnh ve sau :

  • Qua v du hnh 1 , ta thay co nhng t giac noi tiep c va co nhng t giac khong noi tiep c bat k ng tron nao Vay khi nao mot t giac noi tiep c trong mot ng tron ?

  • 1.Khai niem t giac noi tiep :2. nh l : T giac ABCD noi tiep(O) ABCODBai 7:T GIAC NOI TIEP3. nh l ao : ( SGK trang 87 ) Neu mot t giac co tong so o hai goc oi dien bang th t giac o noi tiep c ng tron ( SGK trang 87 )

  • GT KLT giacABCD noi tiep(O) OBCDA

  • OBCDAABCD noi tiep ( O ) A, B, C ( O)D ( O)D nam tren cung m(ABC luon noi tiep c ng tron)la cung cha goc dng tren oan AC la cung cha goc dng tren oan AC A,B,C,D ( O ) ( gt )

  • 1.Khai niem t giac noi tiep :2. nh l : ABCODBai 7:T GIAC NOI TIEP3. nh l ao : (SGK trang 88)T giac ABCD ABCD noi tiep(SGK trang 88)(SGK trang 87)T giacABCD noi tiep(O)

  • CUNG CO : Trong cac hnh ve sau,hnh khong noi tiep c ng tron la : B. Hnh bnh hanh C. Hnh vuong D. Hnh thang can A. Hnh ch nhat

  • PHIEU HOC TAP Cau 1 :Hnh nao sau ay khong noi tiep c ng tron ?a/ Hnh vuong b/ Hnh ch nhat c/ Hnh thoi d/ Hnh thang can Cau 2 :e t giac MNPQ co noi tiep c ng tron th : Cau3 :Trong cac khang nh sau , hay chon khang nh sai Mot t giac noi tiep c neu : a/ T giac co goc ngoai tai nh bang goc trong oi dien b/ T giac co tong hai goc oi dien bang c/ T giac co hai nh ke nhau cung nhn canh cha hai nh con lai di mot goc d/ T giac co tong hai goc bang

  • DN DHc nh ngha, nh l , nh l ao bai T GIAC NOI TIEP BTVN : 54, 55, (SGK/89)

  • Knh chao quy thay coHT