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共回答了19个问题采纳率:78.9% 举报
(1)直线MN的解析式为y=
![](https://img.yulucn.com/upload/6/85/6850e672e4ff5e383ce54a37442e65d9_thumb.jpg)
x+1;
(2)①若∠NMP
1 =90°,则△MOP
1 ∽△FOM,P
1 的坐标为(
![](https://img.yulucn.com/upload/6/85/6850e672e4ff5e383ce54a37442e65d9_thumb.jpg)
,0);
若∠NMP
2 =90°,过N作NH⊥x轴于H,则△NHP
2 ∽△FOM,P
2 的坐标为(
![](https://img.yulucn.com/upload/0/33/033b0ca03c5292992f7a00d792c57b4e_thumb.jpg)
,0);
若∠MP
3 N=90°,则△MOP
3 ∽△FOM,P
3 的坐标为(
![](https://img.yulucn.com/upload/6/5d/65dcb713db6fa5270ac4a7a3e970b19e_thumb.jpg)
,0);
②
![](https://img.yulucn.com/upload/6/5d/65dcb713db6fa5270ac4a7a3e970b19e_thumb.jpg)
<t<
![](https://img.yulucn.com/upload/e/72/e723f8e1335b6433afd98921074b405d_thumb.jpg)
.
试题分析:(1)设点M(x
1 ,y
1 ),N(x
2 ,y
2 ),过点M、N分别作MD⊥BC,NE⊥BC,垂足为D、E,根据已知条件可求出m的值,进而得到直线解析式;
(2)①由(1)知M(0,1),N(5,),设直线MN的解析式y=
![](https://img.yulucn.com/upload/6/85/6850e672e4ff5e383ce54a37442e65d9_thumb.jpg)
x+1与x轴的交点为F,因为直角三角形的斜边不确定,所以要分三种情况分别讨论,求出符合题意的t值,即可求出P的坐标;②由①可知当若∠MPN=90°,P的坐标,进而可求出∠MPN>90°,则t的取值范围.
试题解析:(1)设点M(x
1 ,y
1 ),N(x
2 ,y
2 ),由
![](https://img.yulucn.com/upload/8/2f/82f4fee6b8c4594bdbfcd0d29f7efbf7_thumb.jpg)
,可得x
2 ﹣5x+2﹣2m=0,
则x
1 +x
2 =5①,x
1 •x
2 =2﹣2m②.
过点M、N分别作MD⊥BC,NE⊥BC,垂足为D、E.
∵S
△ MBC =
![](https://img.yulucn.com/upload/e/6c/e6ceb1a6fd6910978b7a6fdc55e26e4f_thumb.jpg)
S
△ NBC ,
∴MD=
![](https://img.yulucn.com/upload/e/6c/e6ceb1a6fd6910978b7a6fdc55e26e4f_thumb.jpg)
NE,即2﹣x
1 =
![](https://img.yulucn.com/upload/e/6c/e6ceb1a6fd6910978b7a6fdc55e26e4f_thumb.jpg)
(x
2 ﹣2),
∴x
1 =﹣
![](https://img.yulucn.com/upload/e/6c/e6ceb1a6fd6910978b7a6fdc55e26e4f_thumb.jpg)
x
2 +
![](https://img.yulucn.com/upload/a/2b/a2be12a379e54be264b23284e7bd2947_thumb.jpg)
③,
③代入①,得x
2 =5,x
1 =0,
代入②,得m=1,
∴直线MN的解析式为y=
![](https://img.yulucn.com/upload/6/85/6850e672e4ff5e383ce54a37442e65d9_thumb.jpg)
x+1;
(2)①由(1)知M(0,1),N(5,),设直线MN的解析式y=
![](https://img.yulucn.com/upload/6/85/6850e672e4ff5e383ce54a37442e65d9_thumb.jpg)
x+1与x轴的交点为F(﹣2,0).
若∠NMP
1 =90°,则△MOP
1 ∽△FOM,
∴
![](https://img.yulucn.com/upload/6/4a/64adadbf4d0a0c3c7ead18325be65b85_thumb.jpg)
,
∴t=
![](https://img.yulucn.com/upload/6/85/6850e672e4ff5e383ce54a37442e65d9_thumb.jpg)
,
∴P
1 的坐标为(
![](https://img.yulucn.com/upload/6/85/6850e672e4ff5e383ce54a37442e65d9_thumb.jpg)
,0);
若∠NMP
2 =90°,过N作NH⊥x轴于H,则△NHP
2 ∽△FOM,
∴
![](https://img.yulucn.com/upload/a/5f/a5fabbd9406219bce17480373c163442_thumb.jpg)
,
∴t=
![](https://img.yulucn.com/upload/0/33/033b0ca03c5292992f7a00d792c57b4e_thumb.jpg)
,
∴P
2 的坐标为(
![](https://img.yulucn.com/upload/0/33/033b0ca03c5292992f7a00d792c57b4e_thumb.jpg)
,0);
若∠MP
3 N=90°,则△MOP
3 ∽△FOM,
∴
![](https://img.yulucn.com/upload/d/24/d244c7b63729d81b85feee991110d8c0_thumb.jpg)
,
∴2t
2 ﹣10t+7=0,
解得:t=
![](https://img.yulucn.com/upload/6/5d/65dcb713db6fa5270ac4a7a3e970b19e_thumb.jpg)
,
∴P
3 的坐标为(
![](https://img.yulucn.com/upload/6/5d/65dcb713db6fa5270ac4a7a3e970b19e_thumb.jpg)
,0);
②由①可知P
3 的坐标为(
![](https://img.yulucn.com/upload/6/5d/65dcb713db6fa5270ac4a7a3e970b19e_thumb.jpg)
,0),
∵∠MPN>90°,
∴
![](https://img.yulucn.com/upload/6/5d/65dcb713db6fa5270ac4a7a3e970b19e_thumb.jpg)
<t<
![](https://img.yulucn.com/upload/e/72/e723f8e1335b6433afd98921074b405d_thumb.jpg)
.
![](https://img.yulucn.com/upload/7/7c/77ceceb97eee1e80376987fe0de50343_thumb.jpg)
.
1年前
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