The clock is a circle divided into 12 equal parts, each part is 360/ 12=30 degrees; At eight o'clock, the hour hand is at eight, and the minute hand is at 12, so (12-8)*30= 120 degrees; Because 90 degrees < 120 degrees < 180 degrees; So the hour hand and the minute hand make an obtuse angle.

An angle greater than the right angle (90) and less than the right angle (180) is called an obtuse angle. Conceptually, an angle greater than a right angle (90) and less than a right angle (180) is called an obtuse angle.

In geometry, an angle is a geometric object composed of two rays with a common endpoint. These two rays are called the edges of an angle, and their common endpoint is called the vertex of the angle. The general angle is assumed to be in Euclidean plane, but it can also be defined in Euclidean geometry.

When the angle changes from 90 to180, the sine value decreases (or increases) with the increase (or decrease) of the angle, and the cosine value decreases (or increases) with the increase (or decrease) of the angle. Tangent value increases (or decreases) with the increase (or decrease) of angle, and cotangent value decreases (or increases) with the increase (or decrease) of angle.

Secant value increases (or decreases) with the increase (or decrease) of angle, and cotangent value increases (or decreases) with the increase (or decrease) of angle.