Hauv kev tshaj tawm no, peb yuav xav txog yuav ua li cas los laij cov cheeb tsam saum npoo ntawm lub voj voos parallelepiped thiab txheeb xyuas cov piv txwv ntawm kev daws teeb meem rau kev kho cov khoom siv.
Cov ntsiab lus
Cov qauv hauv cheeb tsam
Qhov chaw (S) ntawm qhov chaw ntawm lub cuboid yog xam raws li hauv qab no:
S = 2 (ab + bc + ac)
Cov mis yog tau raws li nram no:
- Lub ntsej muag ntawm ib lub voj voog parallelepiped yog cov duab plaub, thiab lub ntsej muag rov qab sib npaug rau ib leeg:
- ob lub hauv paus: nrog sab a и b;
- plaub sab ntsej muag: nrog ib sab ib/b thiab siab c.
- Ntxiv cov cheeb tsam ntawm txhua lub ntsej muag, txhua qhov sib npaug ntawm cov khoom ntawm ob sab ntawm qhov ntev sib txawv, peb tau txais: S = ab + ab + bc + bc + ac + ac = 2 (ab + bc + ac).
Piv txwv ntawm qhov teeb meem
Muab xam qhov chaw saum npoo ntawm ib lub cuboid yog tias nws paub tias nws qhov ntev yog 6 cm, dav yog 4 cm, thiab qhov siab yog 7 cm.
Kev txiav txim siab:
Cia peb siv cov qauv saum toj no, hloov cov txiaj ntsig paub rau hauv nws:
Luas = 2 ⋅ (6 cm ⋅ 4 cm + 6 cm ⋅ 7 cm + 4 cm ⋅ 7 cm) = 188 cm2.