![](https://blog.hocmai.vn/wp-content/uploads/2017/07/hot.gif)
![](https://blog.hocmai.vn/wp-content/uploads/2017/07/hot.gif)
Cho hbh ABCD, góc A < 90 độ . Kẻ CM , CN vuông góc AB, AD. AC cắt MN tại I. Kẻ CH vuông góc MN
a, IM.IN=IA.IC
b, cm [tex]\frac{MN}{CH}= \frac{AM}{CM}+\frac{AN}{CN}[/tex]
c, [tex]AC^2=AM.AB+AN.AD[/tex]
Giúp mình câu b, c ạ
a, IM.IN=IA.IC
b, cm [tex]\frac{MN}{CH}= \frac{AM}{CM}+\frac{AN}{CN}[/tex]
c, [tex]AC^2=AM.AB+AN.AD[/tex]
Giúp mình câu b, c ạ