It's really hard to get without a map. Don't worry about the first question. Then let me look at the second question. I have to introduce it in words.

As can be seen from the figure, the dihedral angle E-AB-D is the angle EAD (drawn directly), and the angle APD= the angle EAD.

So sin angle EAD=sin angle APD=AD/PD, PD= root number (10)*AD, so the value is: root number (10)/ 10.