K
Khách
Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.
Các câu hỏi dưới đây có thể giống với câu hỏi trên
![](https://rs.olm.vn/images/avt/0.png?1311)
BC
9 tháng 9 2016
1.a) xét tam giác DBC có :
góc B = 90 độ ( BD vuông góc BC)
BD=BC
=> tam giác DBC là tam giác vuông cân => góc C =góc BDC= 45 độ
xét hình thang ABCD có :
góc ABC = 360 độ - ( 90 dộ+90 độ+45 độ) = 135 độ
b) ta có :
góc ABD = góc ABC - góc DBC = .135 độ - 90 độ = 45 độ
BD = cos ABD . AB = cos 45 độ . 3 = ......cm
mà BD=BC=> BC =.....cm
xét tam giác vuông cân DBC có
CD^2= BC^2 + BD^2 (định lí pi-ta-go)
<=>.................
<=>.................
Lời giải:
a. $BD\perp BC, BD=BC$ nên tam giác $BDC$ vuông cân tại $B$
$\Rightarrow \widehat{C}=45^0$
$\widehat{ABC}=180^0-\widehat{C}=180^0-45^0=135^0$
b.
Ta có: $\widehat{ABD}=\widehat{ABC}-\widehat{DBC}=135^0-90^0=45^0$ nên tam giác $ABD$ vuông cân tại $A$
$\Rightarrow AD=AB=3$
Áp dụng định lý Pitago:
$BD=\sqrt{AB^2+AD^2}=\sqr{3^2+3^2}=3\sqrt{2}$ (cm)
$BC=BD=3\sqrt{2}$ (cm)
Tam giác $BDC$ vuông cân tại $B$ nên áp dụng định lý Pitago:
$DC=\sqrt{BC^2+BD^2}=\sqrt{(3\sqrt{2})^2+(3\sqrt{2})^2}=6$ (cm)
Hình vẽ:
![](data:image/png;base64,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)