In the diagram, find the size of the angle marked a^\circ
A
60o
B
80o
C
120o
D
160o
Verified Correct Answer: B.
Step-by-Step Mathematical Solution
2 x s = 280^\circ(Angle at centre = 2 x < at circum)
S = \(\frac{280^o}{2}\)
= 140^\circ
< O = 360 - 280 = 80^\circ
60 + 80 + 140 + a = 360^\circ
(< in a quad); 280 + a = 360
a = 360 - 280
a = 80^\circ
Source: Myschool Past Questions Archive (Record #36425)