txheem
Hauv kev tshaj tawm no, peb yuav xav txog cov khoom tseem ceeb ntawm qhov siab ntawm daim duab peb sab isosceles, nrog rau kev txheeb xyuas cov piv txwv ntawm kev daws teeb meem ntawm lub ncauj lus no.
Nco ntsoov: daim duab peb sab hu ua isosceles, yog tias ob ntawm nws sab sib npaug (lateral). Sab thib peb hu ua lub hauv paus.
Altitude khoom nyob rau hauv daim duab peb sab isosceles
Khoom Muaj Khoom 1
Hauv daim duab peb sab isosceles, ob qhov siab tshaj plaws kos rau sab yog sib npaug.
AW = CD
Rov qab lo lus: Yog tias ob qhov altitudes sib npaug hauv daim duab peb sab, ces nws yog isosceles.
Khoom Muaj Khoom 2
Nyob rau hauv daim duab peb sab isosceles, qhov siab qis qis rau lub hauv paus yog tib lub sij hawm lub bisector, qhov nruab nrab, thiab lub perpendicular bisector.
- BD - qhov siab kos rau hauv paus AC;
- BD yog qhov nruab nrab, yog li AD = DC;
- BD yog lub bisector, li no lub kaum sab xis α sib npaug rau lub kaum sab xis β.
- BD - perpendicular bisector rau sab AC.
Khoom Muaj Khoom 3
Yog tias ob sab / kaum ntawm daim duab peb sab isosceles paub, ces:
1. Qhov siab ntev haqis dua ntawm lub hauv paus a, yog xam los ntawm cov mis:
- a - vim li cas;
- b - sab.
2. Qhov siab ntev hbkos rau sab b, sib npaug:
p - qhov no yog ib nrab-perimeter ntawm daim duab peb sab, xam raws li nram no:
3. Qhov siab mus rau sab tuaj yeem pom los ntawm sine ntawm lub kaum sab xis thiab qhov ntev ntawm sab daim duab peb sab:
Nco ntsoov: rau ib daim duab peb sab isosceles, cov khoom siab dav dav uas tau nthuav tawm hauv peb cov ntawv tshaj tawm - kuj siv tau.
Piv txwv ntawm qhov teeb meem
Txoj Haujlwm 1
Ib daim duab peb sab isosceles muab, lub hauv paus yog 15 cm, thiab sab yog 12 cm. Nrhiav qhov ntev ntawm qhov siab txo qis mus rau lub hauv paus.
tshuaj
Cia peb siv thawj cov qauv qhia hauv Khoom Muaj Khoom 3:
Txoj Haujlwm 2
Nrhiav qhov siab kos rau sab ntawm daim duab peb sab isosceles 13 cm ntev. Lub hauv paus ntawm daim duab yog 10 cm.
tshuaj
Ua ntej, peb xam lub semiperimeter ntawm daim duab peb sab:
Tam sim no siv cov qauv tsim nyog rau kev nrhiav qhov siab (sawv cev hauv Khoom Muaj Khoom 3):