Answer:
Step-by-step explanation:
If arccos (√3 / 2) = β, then cos β = adjacent side / hypotenuse = √3 / 2. This tells us immediately that the adjacent side length is √3 and the hypotenuse is 2. Via the Pythagorean Theorem, we know that the third side is 1.
This information rules out the 1st and 3rd answer choices.
Because cos 30° = adj / hyp = √3 / 2, we can conclude that the correct answer is the 4th one: 30°, 60°, 90°
