K
Khách

Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.

5 tháng 5 2016

Đề chưa rõ . ABC có A = 50 độ Nhưng sao lại tính góc A ?

5 tháng 5 2016

hơi vô lí 1 chút coi lại đề nhé pạn ơi

6 tháng 5 2016

áp dụng định lí tổng 3 góc vào tam giác ABC :

TC:A+B+C=180=>B=180-A-C=180-50-30=100

vậy góc B bằng 100 độ

               CHÚC PẠN HỌC TỐT

7 tháng 5 2016

ok CÂU B THÌ MÌNH CHỊU

                      CHÚC PẠN HỌC TỐT

 

10 tháng 5 2016

mình biết làm câu b hề.

*xét tam giác ABH và tam giác DBH có

AH =AD ( giả thuyết )

BH cạnh chung

góc BHA = BHD =90độ

suy ra hai tam giác  trên bằng suy ra góc BDH = BAH ( hai góc tương ứng)

* xét tam giác AHC và BHC có

Hc cạnh chung

AH = HD

và là hai tam giác vuông

suy hai tam giác trên bằng nhau suy ra góc HDC =góc HAC

mặt khác góc BAc =BAH +HAC

                        góc BDC= BDH +HDC

suy ra góc BAC=BDC

còn hình thì bn tự vẽ nha

     

 

10 tháng 5 2016

j liên quan đến toán hình hỏi mình hs lớp 7

 

5 tháng 5 2016

góc b  nhầm

16 tháng 5 2016

a) góc A = 50 độ đề cho

b) biet nhung ko giai

 

17 tháng 7 2016

Ủa, câu a đề cho rồi mà !

15 tháng 6 2022

hảo hán =))

 

15 tháng 6 2022

vaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiivaiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii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

9 tháng 3 2022

a: \(\widehat{A}=180^0-50^0-30^0=100^0\)

b: Xét ΔBAD có 

BH là đường cao

BH là đường trung tuyến

Do đó:ΔBAD cân tại B

Xét ΔCAD có

CH là đường cao

CH là đường trung tuyến

Do đó: ΔCAD cân tại C

Xét ΔBAC và ΔBDC có

BA=BD

AC=DC

BC chung

Do đó:ΔBAC=ΔBDC

Suy ra: \(\widehat{BAC}=\widehat{BDC}\)

10 tháng 5 2016

a)^A=1000 (quá đơn giản,bn tự lm)

b) Xét tam giác BAH=tam giác BDH (2cgv)

=>^BAH=^BDH (cặp góc t.ứ)

và tam giác CAH=tam giác CDH (2cgv)

=>^CAH=^CDH (cặp góc t.ứ)

Ta có:^BAC=^BAH+^CAH

     ^BDC=^BDH+^CDH

mà ^BAH=^BDH(cmt);^CAH=^CDH(cmt)

=>^BAC=^BDC

c)Vì ^ACB<^ABC (300<500)

=>AB<AC

mà HB là hình chiếu của đg xiên AB

  HC là hình chiếu của đg xiên AC

=>HB<HC

11 tháng 12 2018

hính tự vẽ nha

7 tháng 2 2020

Câu hỏi của nguyen anh ngoc ly - Toán lớp 7 - Học toán với OnlineMath

24 tháng 5 2022

a: \(\widehat{C}=90^0-60^0=30^0\)

Xét ΔABC có \(\widehat{C}< \widehat{B}\)

nên AB<AC

Xét ΔABC có AB<AC

mà HB là hình chiếu của AB trên BC

và HC là hình chiếu của AC trên BC

nên HB<HC

b: Xét ΔAHC vuông tại H và ΔDHC vuông tại H có

HC chung

HA=HD

Do đó: ΔAHC=ΔDHC

c: Xét ΔBAC và ΔBDC có 

CA=CD

\(\widehat{ACB}=\widehat{DCB}\)

CB chung

Do đó: ΔBAC=ΔBDC

Suy ra: \(\widehat{BAC}=\widehat{BDC}=90^0\)

24 tháng 5 2022

a: \(\widehat{C}=90^0-60^0=30^0\)

Xét ΔABC có \(\widehat{C}< \widehat{B}\)

nên AB<AC

Xét ΔABC có AB<AC

mà HB là hình chiếu của AB trên BC

và HC là hình chiếu của AC trên BC

nên HB<HC

b: Xét ΔAHC vuông tại H và ΔDHC vuông tại H có

HC chung

HA=HD

Do đó: ΔAHC=ΔDHC

c: Xét ΔBAC và ΔBDC có 

CA=CD

\(\widehat{ACB}=\widehat{DCB}\)

CB chung

Do đó: ΔBAC=ΔBDC

Suy ra: \(\widehat{BAC}=\widehat{BDC}=90^0\)

9 tháng 7 2023

a: góc B=90-30=60 độ

góc B>góc C

=>AC>AB

góc CAH=90-30=60 độ>góc C

=>CH>AH

b: Xét ΔAHC vuông tại H và ΔDHC vuông tại H có

CH chung

HA=HD

=>ΔCAH=ΔCDH

c: Xét ΔACB và ΔDCB có

CA=CD

góc ACB=góc DCB

CB chung

=>ΔACB=ΔDCB

=>góc CDB=góc CAB=90 độ

8 tháng 7 2016
bạn nào giúp mình với
31 tháng 1 2020

Hình tự vẽ

+) Xét \(\Delta ABC\) vuông tại A  có

\(\widehat{B}+\widehat{ACB}=90^o\)  ( tính chất tam giác vuông)

\(\Rightarrow60^o+\widehat{ACB}=90^o\)

\(\Rightarrow\widehat{ACB}=30^o\)

\(\Rightarrow\widehat{ABC}>\widehat{ACB}\)           ( do \(60^o>30^o\)  )

\(\Rightarrow AC>AB\)  (Trong một tam giác, cạnh đối diện với góc lớn hơn là cạnh lớn hơn)

+) Xét \(\Delta ABH\) vuông tại H ta có 

\(\widehat{B}+\widehat{HAB}=90^o\)   ( tính chất tam giác vuông)

\(\Rightarrow60^o+\widehat{HAB}=90^o\)

\(\Rightarrow\widehat{HAB}=30^o\)

+) Ta có AH nằm giữa AC và AB                               ( chỗ này mk ko bt lí giải)

\(\Rightarrow\widehat{HAB}+\widehat{HAC}=\widehat{BAC}\)

\(\Rightarrow\widehat{HAC}+30^o=90^o\)

\(\Rightarrow\widehat{HAC}=90^o-30^o=60^o\)

\(\Rightarrow\widehat{HAC}< \widehat{HAB}\)        ( do \(60^o>30^o\))

\(\Rightarrow CH< HB\)   (Trong một tam giác, cạnh đối diện với góc lớn hơn là cạnh lớn hơn)

b)  Ta có điểm D thuộc tia đối tia HA   (gt)

Mà AH \(\perp\) BC

\(\Rightarrow HD\perp\) BC
\(\Rightarrow\widehat{DHC}=\widehat{AHC}\left(=90^o\right)\)

+) Xét \(\Delta AHC\) vuông tại H và \(\Delta DHC\)  vuông tại H có 

HC: cạnh chung

\(\widehat{DHC}=\widehat{AHC}\)              (cmt)

AH = HD   ( gt)

=> \(\Delta AHC\)\(\Delta DHC\)          ( c- g-c)

c)  +) Theo câu b, ta có    \(\Delta AHC\)=   \(\Delta DHC\)

                      \(\Rightarrow\widehat{ACH}=\widehat{DCH}\)          ( 2 cạnh tương ứng)

                           và AC = AD   ( 2 cạnh tương ứng)

+) Xét \(\Delta DBC\)  và \(\Delta ABC\)  có

BC : cạnh chung

\(\widehat{DCH}=\widehat{ACH}\)         ( cmt)

AD = AC   (cmt)

\(\Rightarrow\Delta DBC=\Delta ABC\)         ( c-g-c)

\(\Rightarrow\widehat{BDC}=\widehat{BAC}=90^o\)            ( 2 cạnh tương ứng)

~ Học tốt

21 tháng 5 2021

bạn ơi sao góc HAC < góc HAB được