Step 1: look at 1:53 and 3:54 and notice that d is connected to that constant pi (or \hat pi), the value of which is not yet found here. Step 2: to see that this constant is indeed pi, go to th-cam.com/video/qT9sxYcImsk/w-d-xo.html where this follows from the Global DeMoivre-Laplace Theorem.
How do we find d?
Step 1: look at 1:53 and 3:54 and notice that d is connected to that constant pi (or \hat pi), the value of which is not yet found here.
Step 2: to see that this constant is indeed pi, go to th-cam.com/video/qT9sxYcImsk/w-d-xo.html where this follows from the Global DeMoivre-Laplace Theorem.