txheem
daim duab peb sab - Qhov no yog daim duab geometric uas muaj peb sab tsim los ntawm kev sib txuas peb lub ntsiab lus ntawm lub dav hlau uas tsis koom nrog tib txoj kab ncaj nraim.
Cov qauv siv dav dav rau kev suav thaj tsam ntawm daim duab peb sab
Lub hauv paus thiab qhov siab
Thaj tsam (S) ntawm daim duab peb sab yog sib npaug rau ib nrab ntawm cov khoom ntawm nws lub hauv paus thiab nws qhov siab.
Heron tus qauv
Mus nrhiav thaj chaw (S) ntawm daim duab peb sab, koj yuav tsum paub qhov ntev ntawm tag nrho nws sab. Nws yog xam raws li nram no:
p - semi-perimeter ntawm daim duab peb sab:
Los ntawm ob sab thiab lub kaum sab xis ntawm lawv
Thaj tsam ntawm ib daim duab peb sab (S) yog sib npaug rau ib nrab ntawm cov khoom ntawm nws ob sab thiab lub sine ntawm lub kaum sab xis ntawm lawv.
Thaj tsam ntawm ib daim duab peb sab
Thaj tsam (S) ntawm ib daim duab yog sib npaug rau ib nrab ntawm cov khoom ntawm nws ob txhais ceg.
Thaj tsam ntawm daim duab peb sab isosceles
Thaj tsam (S) suav nrog cov qauv hauv qab no:
Thaj tsam ntawm ib daim duab peb sab sib npaug
Txhawm rau nrhiav thaj tsam ntawm daim duab peb sab tsis tu ncua (txhua sab ntawm daim duab yog sib npaug), koj yuav tsum siv ib qho ntawm cov qauv hauv qab no:
Los ntawm qhov ntev ntawm sab
Los ntawm qhov siab
Piv txwv ntawm cov dej num
Txoj Haujlwm 1
Nrhiav thaj tsam ntawm daim duab peb sab yog tias ib qho ntawm nws sab yog 7 cm thiab qhov siab kos rau nws yog 5 cm.
Kev txiav txim siab:
Peb siv cov qauv uas qhov ntev ntawm sab thiab qhov siab koom nrog:
S = 1/2 ⋅ 7 cm ⋅ 5 cm = 17,5 cm2.
Txoj Haujlwm 2
Nrhiav thaj tsam ntawm daim duab peb sab uas nws sab yog 3, 4 thiab 5 cm.
1 Kev daws:
Cia peb siv Heron's formula:
Luas = (3 + 4 + 5) / 2 = 6 cm.
Thiaj li, lub
2 Kev daws:
Vim tias daim duab peb sab nrog sab 3, 4 thiab 5 yog ib daim duab plaub, nws thaj chaw tuaj yeem suav nrog cov qauv sib xws:
S = 1/2 ⋅ 3 cm ⋅ 4 cm = 6 cm2.
Koj