Question

I’m not sure how to solve this. Please show how you solve this problem, thank you.

Answer 1

Answer:

Pretend that H is the midpoint of AB, connect O and H

=> OH is the median of ΔOAB

Since we know that OA = OB => ΔOAB is an isosceles triangle

=> OH is also the height of ΔOAB

=> ∠OBA = ∠OAB = (180° - ∠AOB)/2 = (180° - 120°)/2 = 60°/2 = 30°

Now look at ΔOHB (that you create by connecting O and H)

We have:

cos30° = BH/OB

=> BH = cos30° · OB = √3/2 · x = (√3 x)/2

Because we have H as the midpoint of AB, we know that:

AB = 2 · BH = 2 · (√3 x)/2 = √3 x

So the answer is B