Question tip: DE⊥AB,DF⊥AC
Proof: Because AD is the bisector of ∠BAC.
So DE=DF (according to the properties of the angular bisector)
Then S△ABD= 1/2*DE*AB.
S△ADC= 1/2*DF*AC
That is, S△ABD:S△ADC=AB:AC.
Question 12:
It is known that in △ABC and △DEF, AB=DE, BC=EF, AH and DG are the median lines of BC and EF, respectively, while
AH=CG, verification: △ ABC △ def.
It is proved that because BC=EF, AH and DG are the median lines of BC and EF respectively.
So BH=HC=EG=GF.
In △ABH and △DEG,
AB=DE，AH=DG，BH=EG。
so△ABH?△DEG(SSS)
So ∠DGE=∠AHB.
And because ∠ DGF+∠ dge = 90, ∠ AHC+∠ AHB = 90.
So ∠DGF=∠AHC.
At △AHC and △DGF,
∠DGF=∠AHC，AH=DG，HC=GF .
So △ AHC △ DGF (SAS)
So AC=DF
In △ABC and △DEF,
AB=DE，AC=DF，BC=EF。
So △ ABC △ def (SSS) is the conclusion.
How to do the second question on page 26 and the second question on page 27 10 in the eighth grade mathematics of People's Education Press (1) The triangle ABD and the triangle CDB are congruent.
(2) The areas of triangle AFD and triangle ABD and triangle BDC are equal.
10
Equation, using congruence
People's Education Edition, the first volume of mathematics, 27 pages, 12 questions, electronic textbooks, come on.
PEP published 12 of the eighth grade mathematics P 139. If you tell me this time tomorrow afternoon, I'm sure I can help you work it out.
I'm good at math, believe me.
The first item on page 34 of eighth grade mathematics in People's Education Press is on the perpendicular line of AE and BC from point C and point D respectively, and AB=AC=CE, AB+BD=DE can be obtained.
People's education printing plate eighth grade mathematics first volume, examination questions. Baidu has no answer.
Learn to practice the first volume of eighth grade mathematics in the fast lane (PEP). What is this? . .
I also studied the People's Education Edition. There seems to be no such problem. .
Practice the fast lane. . What is this and what. .
There are too many mid-term exam questions and answers in the eighth grade math textbook. Plagiarism may form a habit and have a bad influence on future study. I can't find the answer online.
Get into the habit of thinking seriously now and study hard, even if your answer is wrong, at least you can deepen your impression.
The properties of equilateral triangles are used in the question 1 1 in the first volume of eighth grade mathematics.
And SAS to find ABE congruence ADC.
Then make sure.
How to solve the sixth problem on page 27 of congruent triangles, the first volume of eighth grade mathematics of People's Education Press: It should be built at the intersection of bisectors of three angles.
See page 2 1 of the book, "The points with equal distance from the inside of the corner to both sides of the corner are on the bisector of the corner".