This is the reciprocal version of the 2nd trigonometry trick!

Example:

arcctn(2/1) = 26.56505118...°

arcctn(1/2) = 63.43494882...°

90° - 26.56505118...° = 63.43494882...°

90° - 63.43494882...° = 26.56505118...°

The "arcctn" function tells you how many degrees an angle will be if its cotangent is x/y. Remember that tangents, sines, cosines, & such are all ratios related to the sides & angles of a triangle. That's what trigonometry is all about!