The answers to the review questions at the end of each chapter in the first volume of eighth grade mathematics of People's Education Press (review questions 1 1 2 review questions 13 review questions 14 review questions 15). Review questions 1 1

1, yes

2( 1) Yes

(2) Delta ABF and Delta △BFD are the same height as the bottom, so they are equal.

3、≈ 1 =∠2 ∴∠ 1+∠eca=∠2+∠ecf

∴∠BCA=∠ECD

In △BCA and △ECD, CD = ca ∠ BCA = ∠ ECDEC = BC ∴△ BCA △ ECD ∴ Germany = AB.

4, this question is very simple, just look at the picture.

5.∫d is the midpoint of BC ∴ BD = DC in right-angle △BDE and right-angle △DFC, and be = cfbd = DC ∴△ BDE △ DFC.

∴DE=DF

DE⊥AB, DF⊥AC (the points on the bisector are perpendicular to both sides and equal) ∴AD is the bisector of ∠ABC.

6. Make the median vertical lines of the three roads respectively, and the intersection of the three median vertical lines is the location of the building.

According to the meaning of the question, AC = dbac ‖ db.

∴∠ CAE =∠ DBE in △ACE and △DBF AC = DB.

∠CAE=∠DBE ∠AEC=∠BFD

∴△ ace△ DBF ∴ DF = CE, so they are equal.

8、∫be = cf ∴be+ce=cf+ce ∴bc=ef

In △ABC and △DEF, AB = DE, BC = EF and AC = DF.

∴△ABC≌△DEF ∴∠ABC=∠DEF,∠BCA=∠NFD

∴AB‖DE,AC‖DF

9. According to the meaning of the question, ∠ BEC = 90.

∴∠ BCE+∠ CBE = 90，BCE+∠ ECA = 90。

∴∠ CBE =∠ ECA is in △BCE and △CAD.

∠CBE=∠ECA，∠BEC=∠ADC，BC=AC

∴△BCE≌△CAD ∴CE=AD=2.5cm BE=CD

DE = 1.7 cm ∴ CE-ED = CD 2.5- 1.7 = 0.8.

∴CD=0.8 and CD= become ∴BE=0.8.

That's all I did. I have to work hard myself.

Adopt it