Daim duab peb sab yog daim duab ob sab nrog peb ntug thiab tib tus naj npawb ntawm cov vertices. Nws yog ib qho ntawm cov duab yooj yim hauv geometry. Ib yam khoom muaj peb lub kaum ntse ntse, lawv qhov ntsuas tag nrho yog ib txwm 180 °. Vertices feem ntau txhais los ntawm cov tsiaj ntawv Latin, piv txwv li, ABC.
Theory
Daim duab peb sab tuaj yeem faib raws li cov qauv sib txawv.
Yog tias qhov ntsuas ntsuas ntawm tag nrho nws cov kaum sab xis qis dua 90 degrees, ces nws yog hu ua mob-angled, yog tias ib qho ntawm lawv sib npaug ntawm tus nqi no - duab plaub, thiab lwm yam - obtuse-angled.
Thaum ib daim duab peb sab muaj txhua sab ntawm tib qhov loj, nws yog hu ua equilateral. Nyob rau hauv daim duab, qhov no yog cim nrog ib tug cim perpendicular mus rau ntu. Lub kaum sab xis nyob rau hauv cov ntaub ntawv no ib txwm 60 °.
Yog tias tsuas yog ob sab ntawm daim duab peb sab sib npaug, ces nws hu ua isosceles. Hauv qhov no, cov ces kaum ntawm lub hauv paus yog sib npaug.
Ib daim duab peb sab uas tsis haum ob qho kev xaiv dhau los yog hu ua scalene.
Thaum ob daim duab peb sab hais tias sib npaug, nws txhais tau tias lawv loj tib yamthiab daim ntawv. Lawv kuj muaj cov ces kaum tib yam.
Yog tias tsuas yog ntsuas ntsuas sib npaug, ces cov lej raug hu ua zoo sib xws. Tom qab ntawd qhov sib piv ntawm cov sab sib raug tuaj yeem qhia tau los ntawm qee tus lej, uas yog hu ua coefficient ntawm proportionality.
Ib puag ncig ntawm daim duab peb sab hauv cov ntsiab lus ntawm thaj chaw lossis sab
Raws li nrog rau ib qho polygon, lub cheeb tsam yog qhov sib npaug ntawm qhov ntev ntawm txhua sab.
Rau ib daim duab peb sab, cov qauv zoo li no: P=a + b + c, qhov twg a, b thiab c yog qhov ntev ntawm ob sab.
Tseem muaj lwm txoj hauv kev los daws qhov teeb meem no. Nws muaj nyob rau hauv nrhiav lub perimeter ntawm ib daim duab peb sab los ntawm cheeb tsam. Ua ntej koj yuav tsum paub qhov sib npaug uas cuam tshuam txog ob qhov ntau.
S=p × r, qhov twg p yog lub semiperimeter thiab r yog lub vojvoog ntawm lub voj voog sau rau hauv cov khoom.
Nws yooj yim heev los hloov qhov sib npaug rau hauv daim ntawv peb xav tau. Txais:
p=S/r
Tsis txhob hnov qab tias lub cheeb tsam tiag tiag yuav loj dua qhov tau txais 2 npaug.
P=2S/r
Qhov no yog qhov piv txwv yooj yim li qhov no daws tau.
