
Tracy D. answered 09/17/20
Upbeat, patient Math Tutor investing in students to succeed
So this is a Trig question on one of the special triangles.
Note: It is to your advantage to become familiar with both the 30-60-90 and the 45-45-90 triangles, that way you will not have to memorize the whole unit circle.
If you make a 30-60-90 triangle, and pretend to stand at the 30° angle, when you look straight across you will intersect with the leg opposite the 30°, and that is where you will put a "1" for the leg length, moving counter clock wise, you will put a "2" for the hypotenuse leg and finally you will put a √3, for the adjacent (base) leg.
Cosine = (adjacent/hypotenuse), you are looking for (√3/2); you will quickly see the acute angle is the 30º angle.