Answer:
The answer is option 2.
Step-by-step explanation:
Using Cosine Rule, c² = a²+b²-2(a)(b)cosθ where a,b and c represents the side length :
Let a = AD = 5 units (radius),
Let b = BD = 5 units (radius),
Let c = AB,
Let θ = 100°,
c² = 5² + 5² - 2(5)(5)cos 100°
c² = 50 - 50cos 100°
c² = 58.68
c = √58.68
= 7.7 units (near. tenth)
