And we check to see the three areas are indeed 1/3 Pi (2R) R^2 = 4.18879 R^2. They are!!!

Input := 


Area1[R1sol]//N

Output =


         2

4.18879 R

Input := 


Area2[R1sol,R2sol]//N

Output =


         2

4.18879 R

Input := 


Area3[R2sol]//N

Output =


         2

4.18879 R