Question 8. Through calculation, it is known that when AR is perpendicular to BC, EF is the shortest, and D is excluded; You can calculate the analytical formula y= root number x 2-2x+4, excluding a, it is definitely not a straight line; Calculate the length of EF (divided by 2) when R and C coincide. We know that EF is about 1.5, so we choose C.

Question 22: Graphics should be able to be drawn. You can turn it into seven equilateral triangles (BE2, AE 1, CE3) by bisecting the edge, which is the simplest. Other transfer methods have to be deleted and supplemented before they can come out.