The goal and evaluation of eight chapters and two chapters of mathematics in Zhejiang Education Press

6.△ADE is an isosceles triangle; Because AC = BC, △ AC=BC is an isosceles triangle; So angle a = angle b;

Because DE is parallel to BC, angle EDA = angle B, so angle EDA = angle A; So △ADE is an isosceles triangle;

7.( 1) Because DG = EF and DC = BE, Rt△CDG is equal to Rt△BEF；; ; So CG = BF

So CG-GF=BF-GF So: CF = BG.

(2) Because BG=CF and DG = EF, Rt△BDG is all equal to Rt△CEF；; ; So BD = ce

8. Set the angle to o; Because bo = 0.7 and ab = 2.5, ao = (2.5 square -0.7 square) root = 2.4;

So a1o = 2.4-0.4 = 2; So B 1o = (2.5 square -2 square) root =1.5;

So b moves outward: 1.5-0.7 = 0.8.