I was wondering if anyone of you guys know how to calculate the left angle in a triangle knowing the horizontal and vertical length and height of the triangle

and then how to convert the formula to python

In my math book it says that to calculate the angle you have to divide the height with the lenght and then INV the answer then press tan on the calculator to get the angle

Can python use this INV button and what does it stand for and do

Why do I need this well so I can animate 180 degress rotation animation of the arm from pointing upforward to downforward knowing the angle of the enemy and then rotate the arms to that precise angle