Faid arc
Tha cearcall-thomhas cearcaill = \(\pi d\) no \(2\pi r\).
Seall air seactor a' chearcaill gu h-矛osal. Gus faid an arc obrachadh a-mach, feumaidh fios a bhith againn d猫 a' bhloigh dhen chearcall a th' air a sealltainn. Gus seo a dh猫anamh, bidh sinn a' cleachdadh a' che脿irn agus ga choimeas ri 360藲.
Tha 144掳 sa che脿rn seo.
Sin \(\frac{{144^\circ }}{{360^\circ }} = \frac{2}{5}\) de char sl脿n (360掳).
Mar sin 's e an arc \(\frac{2}{5}\) a' chearcaill-thomhais.
\(c=\pi d=3.14\times 6\) (Cuimhnich gu bheil an cearcall-thomhas a dh脿 uiread ris an radius.)
\(=18.84\,cm\)
Faid an arc = \(\frac{2}{5}\times 18.84 = 7.54\,cm\)
(Chan fheum thu \(\frac{144}{360}\) a sh矛mpleachadh. Faodaidh tu seo a chleachdadh ann a bhith ag obrachadh a-mach an arc an 脿ite \(\frac{2}{5}\).)
'S e am foirmle airson Faid an Arc obrachadh a-mach:
\(Faid\,arc = \frac{{\text{Ce脿rn}}}{{360^\circ }} \times \pi d\)
Feuch a-nis a' cheist gu h-矛osal.
Question
Obraich a-mach faid an arc san diagram gu h-矛osal.
\(Faid\,arc = \frac{{\text{Ce脿rn}}}{{360^\circ }} \times \pi d\)
Cuimhnich cuideachd gu bheil \(d = 2 \times r\)
\(= \frac{{150}}{{360}} \times \pi \times 8\)
\(= 10.47\,cm\)
\(= 7.5\,(gu\,1\,id)\)