In a triangle, we use terms like adjacent and opposite. These refer to sides in relation to angles. In our musical triangle, the drummer is at one angle in the back. This side, where the audience is, is called the opposite side.
Trunc is database function, try using round for numeric values, or change the Processing of Query to database.
Both ACOS and COS are trigonometric functions. The ACOS function returns the angle, in radians, whose cosine is the specified float expression. The COS function returns the cosine of the specified angle, in radians, based on the float expression.