tolong dijawab matematika tentang sudut lingkaran nomor 5 sama nomor 6

jawab
5. BC = OC = OB = sama sisi
<BOC = 1/3 (180) = 60
<BAC = 1/2 <BOC = 1/2 (60) = 30

6. 
α: β = 5. 4
α = 5a
β= 4a

α+ β = 90
5a+4a =  90
9a = 90
a = 10
α = 5a = 50
β = 4a = 40
α- β = 50- 40 = 10