Nws tsis yog qhov xav tsis thoob uas thaum peb pib delve rau hauv cov lus ntawm geometry, peb nug peb tus kheej:Dab tsi yog ib qho ncig?, thiab Dab tsi yog nws lub zog ?; ntawm no hnub no, peb yuav hais ntev txog cov ncauj lus no, koom nrog peb.

## Koj puas paub ib ncig ntawm yog dab tsi?

Raws kev hais lus, nws muaj peev xwm txhais qhov ib puag ncig raws li kab kaw ntawm kab nkhaus thiab flattened uas cov ntsiab lus sib npaug los ntawm nruab nrab taw tes; uas yog nyob rau hauv tib lub dav hlau. Piav qhia hauv cov lus yooj yooj yim; peb tuaj yeem nkag siab nws raws li kev teeb tsa cov ntsiab lus uas muaj nyob hauv lub dav hlau, ntawm tib qhov deb ntawm qhov chaw.

### Vajvoog lossis ncig?

Feem ntau yuav, thaum koj hnov ​​cov lus no, koj xav txog cov lus ua; txij li nyob rau hauv lub neej txhua hnub, lawv tau siv nyob rau hauv txoj kev no, tab sis qhov tseeb yog qhov lawv tsis txhawj xeeb zoo ib yam. Cia peb pom, raws li qhov kev xav, lub voj voog yog qhov chaw geometric tsim los ntawm cov ntsiab lus uas ua lub voj voog; Hauv cov lus yooj yooj yim, qhov ncig yog tsim ib puag ncig ntawm lub voj voog.

## Ntsiab lus ntawm lub voj voog

Peb twb teb thawj lo lus nug lawm, tab sis peb tseem tshuav ntau yam yuav piav, yam li yog Lub vojvoog ncig ntawm lub voj voog yog dab tsi?, lossis Dab tsi yog lub cheeb ntawm ib ncig?; Cia peb pom nws cov ntsiab hauv kev nthuav dav:

### chaw

Thaum peb hais txog lub chaw nruab nrab, peb txhais tau tias yog qhov nruab nrab ntawm qhov ncig; Qhov no yog nyob hauv nruab nrab ntawm nws, ntawm qhov kev sib txig sib luag los ntawm qhov seem ntawm cov ntsiab lus ntawm kab ntawv uas ua nws nce. Ntawm qhov no, nws yog qhov muaj peev xwm kos ib qho kawg ntawm cov kab, uas tso cai kom txhais tau qhov seem ntawm nws cov ntsiab; ntxiv rau, rho tawm ntu ntu uas tso cai rau ntsuas qhov ntev, cov ces kaum thiab sib npaug.

### xov tooj cua

Radius yog txhua txoj kab uas koom nrog qhov nruab nrab nrog ntug; Qhov no yog lub hauv paus pib ob qho tib si rau qhov xwm txheej ntawm qhov ncig thiab rau lub voj voos, vim nws tso cai rau peb los laij ntau ntau qhov ntau. Raws li peb hais hauv seem dhau los, qhov kev ncua deb ntawm nruab nrab thiab ib qho taw tes ntawm ntug yuav zoo ib yam; yog li ntawd, tsis muaj teeb meem los ntawm qhov twg taw tes ntawm txoj kab, txoj kab hluav taws xob yuav ntsuas ib txwm zoo ib yam.

Lub vojvoog tsuas yog ib nrab ntawm txoj kab uas hla, thiab yog tias peb xav kom suav lub vojvoog rau ib lub voj voog tshwj xeeb, peb yuav tsum faib qhov nrug nrog 2 pi; nyob rau hauv txoj kev no r = D / 2n.

### Txoj kab uas hla

Txoj kab uas hla yog qhov yooj yim dua ob zaug ntawm lub vojvoog, uas yog; ib kab twg uas hla lub voj voog nyob hauv nws tus kheej thiab muab nws faib ua ob seem. Ib zaug ntxiv, vim hais tias qhov kev ncua deb ntawm nruab nrab thiab lub ntug yog tib yam rau txhua cov ntsiab lus; tsis muaj teeb meem ntau npaum li cas txoj kab kos, lub taub yuav ib txwm zoo ib yam rau ib puag ncig muab.

Yog tias koj xav nthuav cov ncauj lus, peb xav kom koj nyeem peb cov ntawv sau rau dab tsi yog lub taub, qhov twg koj yuav pom cov ntsiab lus ntawm nws.

### Hlua

Zoo heev, peb twb piav txog qhov zoo ntawm cov khoom; tab sis, peb tseem muaj qee cov lus nug los teb, piv txwv:Dab tsi yog lub chord hauv ib ncig? Thaum peb hais txog chord, peb hais txog txoj kab uas koom nrog ob lub ntsiab lus ntawm ntug; tab sis, tsis zoo li lub taub, uas yuav tsum tau dhau ntawm qhov nruab nrab ntawm qhov ncig, ib lub chord tsis tas ua kom tau raws li qhov xav tau no.

### Cov kab tseem ceeb

Ib zaug ntxiv, peb los hla ib lub tswvyim zoo ib yam li lub vojvoog, taub, thiab chord; txij li ib txoj kab sib tsoo yog ib txoj kab uas hla ib ncig ib puag ncig, tab sis nrog qhov muaj npe tsis sib xws uas nws tsis nyob hauv nws txwv; ib txoj kev ncaj ncaj kov yeej qhov teeb meem ntug thiab ua rau "txiav". Nws yog ib qho tseem ceeb uas yuav ua rau qhov sib txawv, txij li lo lus secant los ntawm Latin "kev nyab xeeb", uas txhais tau tias kev txiav.

### Kab Tangent

Ntawm qhov tod tes, peb siv lub sij hawm tangent xa mus rau cov kab uas ua rau muaj kev sib cuag nrog ib ncig ntawm ib qho taw tes, thiab uas tau muab tso nrog qhov sib nrug rau lub vojvoog. Txoj kab ncaj nraim no muaj qhov peculiarity uas nws nyob rau sab nraud; Tsis tas li ntawd, nws qhov loj tuaj yeem sib txawv, txawm hais tias qhov feem ntau tshaj plaws yog tias nws tsis tshaj lub vojvoog.

### Hneev

Thaum kawg, tsuas paub tsis paub uas tseem nyob rau peb kom tshab txhais Arc ntawm ib ncig yog dab tsi? Peb hais txog arcs thaum ob kab raug kos ntawm ib ncig thiab muab faib ua ob ntu; ntu txuas rau ob ntu yog hu ua chord.

## Circumference ntev

Qhov saum toj no, nws tau raug qhia meej meej tias lub voj voog thiab ncig tsis yog nruj me ntsis rau tib yam; ntawm no peb yuav tham txog lwm qhov tseem ceeb sib txawv, thiab qhov ntawd yog qhov kawg, tsis zoo li lub voj voos, tsis muaj thaj chaw, tsuas ntev. Thaum peb hais txog qhov ntev ntawm ib ncig, peb hais txog qhov ntev ntawm txoj kab ntu uas muaj qhov loj me me li qhov no; ua kev xav tias lub voj voog tuaj yeem txuas ntxiv rau ib kab.

Yog tias peb paub qhov ntev ntawm lub vojvoog thiab lub cheeb, nws muaj peev xwm suav qhov ntev, uas tau qhia tias "L”; Cia saib dab tsi yog cov qauv rau nws:

• Luas = 2 x xr: nyob rau hauv cov ntaub ntawv no "r”Puas yuav xov tooj cua.
• L = tau xd: Rau lwm cov tes, nyob rau hauv cov qauv no peb yuav tsum “d”Yog lub taub.

Peb muaj tias cov kev faib ua feem uas muaj nyob nruab nrab ntawm qhov ncig thiab txoj kab uas hla, yog qhov xwm yeem, uas tau sawv cev rau hauv cov ntaub ntawv no los ntawm cov cim ntawm Pi. Qhov no tsis muaj dab tsi ntxiv thiab tsis muaj dab tsi tsawg tshaj li ib qhov tseem ceeb tshaj plaws thiab muaj lub luag haujlwm ntawm qhov tseem ceeb hauv ntau qhov kev suav thiab kev ua lej, kev tawm dag zog thiab ntau qhov chaw, xws li cov xwm txheej ntawm engineering.

Pi muaj cov nqi nyob ib ncig ntawm 3.141592, tab sis nyob rau hauv feem ntau suav, tsawg tus nqi raug coj; siv 3.1416 thiab suav nrog, hauv ntau qhov koj tsuas yog coj 3.14. Cov nqi no muaj nws pib nrog Greek Greek kev ua lej Archimedes; leej twg pom tus nqi ntawm Pi ntawm 3 + 1/7, lossis dab tsi yog sib npaug ntawm 3 + 10/71.

Peb cia siab tias koj nyiam peb cov ntawv thiab nws yuav pab koj daws koj cov kev ua xyem xyav dab tsi yog ib ncig; Ib yam li ntawd, raws li peb paub tias qhov no yog lub ncauj lus uas nkag siab yooj yim dua nrog kev pom piv txwv, ntawm no peb yuav tso koj cov vis dis aus txog qhov ncig.