Recall that for n e n, we define n! , called "n factorial," by n! = n(n − 1)(n-2)(n-.2.1. prove that 1+ žj. = (n + 1), for all n en

Asource of laser light sends rays ab and ac toward two opposite walls of a hall. the light rays strike the walls at points b and c, as shown below: what is the distance between the walls?