txheem
convex quadrilateral - Qhov no yog daim duab geometric tau los ntawm kev txuas plaub lub ntsiab lus ntawm lub dav hlau uas yuav tsum tsis txhob dag ntawm ib txoj kab ncaj nraim. Nyob rau hauv cov ntaub ntawv no, lub sab tsim nyob rau hauv no txoj kev yuav tsum tsis txhob sib tshuam.
Cov qauv hauv cheeb tsam
Raws li cov diagonals thiab lub kaum sab xis ntawm lawv
Thaj tsam (S) ntawm convex quadrilateral yog sib npaug rau ib thib ob (ib nrab) ntawm cov khoom ntawm nws kab pheeb ces kaum thiab lub sine ntawm lub kaum sab xis ntawm lawv.
Ntawm plaub sab (Brahmagupta tus qauv)
Txhawm rau siv cov qauv, koj yuav tsum paub qhov ntev ntawm txhua sab ntawm daim duab. Nws kuj tseem tuaj yeem piav qhia txog lub voj voog nyob ib ncig ntawm lub quadrilateral.
p - semi-perimeter, xam raws li hauv qab no:
Raws li lub vojvoog ntawm lub voj voog inscribed thiab sab
Yog tias lub voj voog tuaj yeem sau rau hauv plaub fab, nws thaj chaw tuaj yeem suav nrog cov qauv:
S = p ⋅ r
r yog lub vojvoog ntawm lub voj voog.
Piv txwv ntawm qhov teeb meem
Nrhiav thaj tsam ntawm lub convex quadrilateral yog tias nws cov kab pheeb ces kaum yog 5 cm thiab 9 cm thiab lub kaum sab xis ntawm lawv yog 30 °.
Kev txiav txim siab:
Peb hloov cov txiaj ntsig u1bu2bknown rau peb rau hauv cov qauv thiab tau txais: S u5d 9/30 * 11,25 cm * XNUMX cm * sin XNUMX ° uXNUMXd XNUMX cm2.