Ini soal matematika kelas 8 tolong di bantu yaah pakai caranya,,,

Ini soal matematika kelas 8 tolong di bantu yaah pakai caranya,,,

⇔busur AB = $frac{ alpha }{360 drjt}$ × 2πr
busur AB = $frac{105}{360}$ × 2 × $frac{22}{7}$ × 12
busur AB = 22 cm (a)

⇔busur AB = $frac{ alpha }{360}$ × 2πr
38,5 = $frac{ alpha }{360}$ × 2 × $frac{22}{7}$ × 10,5
$alpha$ = $frac{38,5 *60}{11}$
$alpha$ = 210 derajat (b)

⇔ PQ = $frac{ alpha }{360}$ 2πr
$3 frac{3}{4} pi$ = $frac{54}{360}$ 2r
$frac{15}{4} pi$ = $frac{3}{10}$ r
$frac{15*10}{4*3}=rto frac{150}{12}$
$12 frac{1}{2}$ cm = r (b)