# Python Exercise 7: Trig functions (15 minutes)

The quantity theta, or the angle that the beam makes with the z-axis, is calculated by:

$\theta = \arctan\left(\frac{p_{T}}{p_{z}}\right)$

The units are radians. Revise your script to include a histogram of theta.

Note

I’ll make your life a little easier: the math function you want is ROOT.TMath.ATan2(y,x), which computes the arctangent of y/x. It’s better to use this function than ROOT.TMath.ATan(y/x), because the ATan2 function correctly handles the case when x=0.