Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.
hình tự vẽ:
xét hai tam giác vuông ABE và DBE:
ab=ad(gt); be là cạnh huyền chung
=>\(\Delta\) ABE = \(\Delta\)DBE
mình sẽ giải tiếp
a) theo đinh j lý pitago : tam giác abc vuông tại A
=> \(AB^2+AC^2=BC^2\)THAY SỐ TA ĐƯỢC \(5^2+7^2=BC^2\) TA ĐƯỢC \(74=BC^2\) =>BC =
8.6023
a) Vì tam giác BAC vuông tại A
=> AB^2 + AC^2 = BC^2 ( đl pytago )
=> BC^2 = 5^2 + 7^2 = 74
=> BC = căn bậc 2 của 74
b)
Xét tam giác ABE; tam giác DBE có :
AB = DB ( gt)
góc ABE = góc DBE ( gt)
BE chung
=> tam giác ABE = tam giác DBE (c.g.c) - đpcm
c)
Vì tam giác ABE = tam giác DBE (câu b)
=> AE = DE
Xét tg AEF ⊥ tại A; tg DEC ⊥ tại D:
AE = DE (c/m trên)
g AEF = g DEC (đối đỉnh)
=> tg AEF = tg DEC (cgv - gn) - đpcm
=> EF = EC
d)
Do tam giác AEF = tam giác DEC (câu c)
=> AE = DE
=> E ∈ đường trung trực của AD (1)
Lại do AB = BD (gt)
=> B ∈ đường trung trực của AD (2)
Từ (1) và (2) => BE là đường trung trực của AD. - đpcm
a) Áp dụng pytago .
b) Xét t/g ABE; tg DBE:
AB = DB ( gt)
g ABE = DBE (suy từ gt)
BE chung
=> tg ABE = tg DBE (c.g.c)
c) Vì tg ABE = tg DBE (câu b)
=> AE = DE
Xét tg AEF ⊥⊥ tại A; tg DEC ⊥⊥ tại D:
AE = DE (c/m trên)
g AEF = g DEC (đối đỉnh)
=> tg AEF = tg DEC (cgv - gn)
=> EF = EC
d) Do tg AEF = tg DEC (câu c)
=> AE = DE
=> E ∈∈ đg trung trực của AD (1)
Lại do AB = BD (gt)
=> B ∈ đg trung trực của AD (2)
Từ (1) và (2) => BE là đg trung trực của AD.
- 544rrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhtttttrfffffffffffffffffffffffffffffffffffrrrrrrrrrrrrrrreeeeeeeeeeeeeeeeeeeeeennnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnn
a: Xét ΔBAE vuông tại A và ΔBDE vuông tại D có
BE chung
BA=BD
=>ΔBAE=ΔBDE
b: ΔBAE=ΔBDE
=>AE=DE
c: Xét ΔBDF vuông tại D và ΔBAC vuông tại A có
BD=BA
góc B chung
=>ΔBDF=ΔBAC
=>BF=BC
=>ΔBFC cân tại B
mà BN là trung tuyến
nên BN là phân giác của góc FBC
mà BE là phân giác của góc ABE
nên B,E,N thẳng hàng
a) tam giác ABC vuông tại A
=> AB2 + AC2 = BC2
=> 52 + 72 = BC2
=> BC2 = 25 + 49 = 74
=> BC = \(\sqrt{74}cm\)
hình như bn ghi sai đề rùi làm sao làm bài b) !!!!!!!1
7756
a, xét tam giác ABC theo định lý py _ta _go ta có :
\(^{BC^2=AC^2+AB^2}\)
\(BC^2=5^2+7^2\)
\(^{BC^2=25+49}\)
\(^{BC^2=74}\)
BC=\(\sqrt{74}\)
b,xét tam giác vuông ABE và tam giác vuông DBE ta có:
BA=DB(gt)
BE chung
=}tam giác ABE=tam giác DBE(ch_cgv)
=}EA=ED (2 cạnh tương ứng)
c,xét tam giác vuông AEF và tam giác vuông DEC ta có:
AE=ED(cm câu b)
E1=E2 (đối đỉnh)
=}tam giác AEF và tam giác DEC (gn_cgv)
=}EF=EC (2 cạnh tương ứng)
d,Ta có :BA =DA (gt)
AE=ED(cm câu a)
=}BE là đường trung trực của AD
MÌNH TỰ LÀM KHÔNG BIẾT CÓ ĐÚNG HAY KHÔNG BẠN Ạ
a) Xét tam giác ABC vuông tại A
có: \(AB^2+AC^2=BC^2\) ( py - ta - go )
thay số: \(5^2+7^2=BC^2\)
\(BC^2=74\)
\(\Rightarrow BC=\sqrt{74}\)cm
b) Xét tam giác ABE vuông tại A và tam giác DBE vuông tại D
có: AB = DB ( gt)
AE là cạnh chung
\(\Rightarrow\Delta ABE=\Delta DBE\left(ch-cgv\right)\)
c) ta có: tam giác ABE = tam giác DBE ( phần b)
=> AE = DE ( 2 cạnh tương ứng)
Xét tam giác AEF vuông tại A và tam giác DEC vuông tại D
có: AE = DE ( cmt)
góc AEF = góc DEC ( đối đỉnh )
\(\Rightarrow\Delta AEF=\Delta DEC\left(cgv-gn\right)\)
=> EF = EC ( 2 cạnh tương ứng)
d) ta có: tam giác ABE = tam giác DBE ( phần b)
=> góc ABE = góc DBE ( 2 góc tương ứng )
Xét tam giác ABH và tam giác DBH
có: AB = DB ( gt)
góc ABE = góc DBE ( cmt)
BH là cạnh chung
\(\Rightarrow\Delta ABH=\Delta DBH\left(c-g-c\right)\)
=> AH = DH ( 2 cạnh tương ứng ) (1)
góc AHB = góc DHB ( 2 góc tương ứng )
mà góc AHB + góc DHB = 180 độ ( kề bù)
=> góc AHB + góc AHB = 180 độ
2. góc AHB = 180 độ
góc AHB = 180 độ :2
góc AHB = 90 độ
=> \(\Rightarrow BE\perp AD⋮H\) ( định lí vuông góc) (2)
Từ (1) ; (2) => BE là đường trung trực của AD ( định lí đường trung trực)