Hauv kev tshaj tawm no, peb yuav xav txog ib qho ntawm cov ntsiab lus tseem ceeb hauv chav kawm 7 geometry - txog lub kaum sab nraud ntawm daim duab peb sab. Peb tseem yuav txheeb xyuas cov piv txwv ntawm kev daws teeb meem txhawm rau txhawm rau sib sau cov ntaub ntawv nthuav tawm.
Txhais ntawm lub kaum sab nraud
Ua ntej, cia peb nco ntsoov tias lub kaum sab nraud yog dab tsi. Cia peb hais tias peb muaj daim duab peb sab:
Nyob ib sab ntawm lub kaum sab hauv (λ) lub kaum sab xis ntawm tib vertex yog lwm. Hauv peb daim duab, nws tau qhia los ntawm tsab ntawv γ.
Qhov twg:
- cov sum ntawm cov ces kaum yog 180 degrees, piv txwv li c+ Luas = 180° (cov khoom ntawm lub kaum sab xis);
- 0 и 0.
Nqe lus ntawm lub theorem
Lub kaum sab nrauv ntawm daim duab peb sab yog sib npaug rau qhov sib npaug ntawm ob lub kaum sab xis ntawm daim duab peb sab uas tsis nyob ib sab ntawm nws.
c = ib + b
Los ntawm qhov kev xav no nws ua raws li lub kaum sab nraud ntawm daim duab peb sab yog ntau dua ib qho ntawm cov ces kaum sab hauv uas tsis nyob ib sab ntawm nws.
Piv txwv ntawm cov dej num
Txoj Haujlwm 1
Ib daim duab peb sab yog muab nyob rau hauv uas qhov tseem ceeb ntawm ob lub kaum sab xis paub - 45 ° thiab 58 °. Nrhiav lub kaum sab nrauv uas nyob ib sab mus rau qhov tsis paub lub kaum sab xis ntawm daim duab peb sab.
tshuaj
Siv cov qauv ntawm lub theorem, peb tau txais: 45 ° + 58 ° = 103 °.
Txoj Haujlwm 1
Lub kaum sab nraud ntawm daim duab peb sab yog 115 °, thiab ib qho ntawm cov kaum sab hauv tsis nyob ib sab yog 28 °. Xam cov nqi ntawm cov kaum sab xis ntawm daim duab peb sab.
tshuaj
Txhawm rau kom yooj yim, peb yuav siv cov cim qhia hauv cov duab saum toj no. Lub kaum sab hauv paub yog coj li α.
Raws li lub theorem: β = γ – α = 115° – 28° = 87°.
lub λ yog nyob ib sab mus rau sab nrauv, thiab yog li xam los ntawm cov qauv hauv qab no (raws li los ntawm cov cuab yeej ntawm lub ces kaum sab nraud): λ = 180 ° - γ = 180 ° - 115 ° = 65 °.