1 . 完成下列推理过程
已知:∠C+∠CBD=180°,∠ABD=85°,∠2=60°,求∠A的度数.
![](https://img.xkw.com/dksih/QBM/editorImg/2023/2/1/296d81d0-825e-4d23-a2a5-2aa7770567ce.png?resizew=183)
解:∵∠C+∠CBD=180°(已知)
∴DB∥CE( )
∴∠1= ( )
∵∠2=∠3( )
∴∠1=∠2=60° ( )
又∵ ∠ABD=85°(已知)
∴∠A=180°-∠ABD-∠1= (三角形三内角和为180°)
已知:∠C+∠CBD=180°,∠ABD=85°,∠2=60°,求∠A的度数.
![](https://img.xkw.com/dksih/QBM/editorImg/2023/2/1/296d81d0-825e-4d23-a2a5-2aa7770567ce.png?resizew=183)
解:∵∠C+∠CBD=180°(已知)
∴DB∥CE( )
∴∠1= ( )
∵∠2=∠3( )
∴∠1=∠2=60° ( )
又∵ ∠ABD=85°(已知)
∴∠A=180°-∠ABD-∠1= (三角形三内角和为180°)
您最近一年使用:0次
2020-06-09更新
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144次组卷
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2卷引用:四川省达州市大竹县杨家中学2022-2023学年七年级下学期期中数学试题
2 . 【问题呈现】
小明在学习中遇到这样一个问题:
如图1,在
中,
,
平分
,
于D,猜想
、
、
的数量关系.
、
的值求
值,得到下面几组对应值:
上表中
____,于是得到
与
、
的数量关系为____.
【变式应用】
(2)小明继续研究,在图2中,
,
,其他条件不变,若把“
于D”改为“F是线段
上一点,
于D”,求
的度数,并写出
与
、
的数量关系:
【思维发散】
(3)小明突发奇想,交换B、C两个字母位置,在图3中,若把(2)中的“点F在线段
上”改为“点F是
延长线上一点”,其余条件不变,当
,
时,∠F度数为____°.
【能力提升】
(4)在图4中,若点F在
的延长线上,
于D,
,
,其余条件不变,从别作出
和
的角平分线,交于点P,试用 x、y表示
____.
小明在学习中遇到这样一个问题:
如图1,在
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/454632386282b17f21b982cb7e760510.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/68a83fdd2ba72a2dba0b6b10bb3e06b9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7cbce11aa19b8bd2bf6ee5a834e005de.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8b5f215a42c4b7078d8d65923eb9980e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/febc9a89d0d1c97b88c0f4acd32b4e67.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/194741f4d2ae7ee44cafca780361446a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1e37b078d02601f76f0f8320b410809f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/febc9a89d0d1c97b88c0f4acd32b4e67.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/194741f4d2ae7ee44cafca780361446a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1e37b078d02601f76f0f8320b410809f.png)
![]() | 10 | 30 | 30 | 20 | 20 |
![]() | 70 | 70 | 60 | 60 | 80 |
![]() | 30 | a | 15 | 20 | 30 |
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/380bbacf854e30e2e747fc286d2b9997.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1e37b078d02601f76f0f8320b410809f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/febc9a89d0d1c97b88c0f4acd32b4e67.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/194741f4d2ae7ee44cafca780361446a.png)
【变式应用】
(2)小明继续研究,在图2中,
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/19766bbdc2d23ae20e9f34530c3a1543.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/991d28fec5464134cececebc681e54ab.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8b5f215a42c4b7078d8d65923eb9980e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/68a83fdd2ba72a2dba0b6b10bb3e06b9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6c4567ae3f7827588855f39569d4f7c5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f6c19410c7abeae002ca97cfad4c791f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f6c19410c7abeae002ca97cfad4c791f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/febc9a89d0d1c97b88c0f4acd32b4e67.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/194741f4d2ae7ee44cafca780361446a.png)
【思维发散】
(3)小明突发奇想,交换B、C两个字母位置,在图3中,若把(2)中的“点F在线段
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1642eec556eb252de9c1ab7bb5ca90b3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4eb637b38d3017f0d2deeec358896902.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7470b23c2dfe3c1404d6cb0ea762f3c8.png)
【能力提升】
(4)在图4中,若点F在
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/68a83fdd2ba72a2dba0b6b10bb3e06b9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6c4567ae3f7827588855f39569d4f7c5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7d6a5d91c35bf548b368a5c1ae8712cb.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7d4b76647dcfb6c6beaa81fb23fed576.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/35803969509655f72b4118503ae1c966.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c962fe4f47732b8e6e83d17ff2b9af13.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8b6fede7d2da3ccecf3f9d32a10346c3.png)
您最近一年使用:0次
2022-12-09更新
|
439次组卷
|
6卷引用:江苏省徐州市2022-2023学年七年级下学期期中数学试题