In the diagram, find the size of the angle marked a°
A.
60o
B.
80o
C.
120o
D.
160o
Correct answer is B
2 x s = 280°(Angle at centre = 2 x < at circum)
S = \(\frac{280^o}{2}\)
= 140°
< O = 360 - 280 = 80°
60 + 80 + 140 + a = 360°
(< in a quad); 280 + a = 360
a = 360 - 280
a = 80°