a: Xét ΔAHB và ΔAHC 

Ta có

AH chung

HB=HC

AB=AC

Suy ra ΔAHB=ΔAHC

Tỉ lệ nghịch là 2 đại lượng đối nghịch nhau, kiểu như cái này tăng thì cái kia giảm (tc thì xét tích tương ứng). - Tỉ lệ thuận là 2 đại lượng cùng tăng và cùng giảm (tc thì xét tỉ số).

Tom and Jerry went through many phases and took place from anywhere from inside a house, to anywhere in outer space. The series includes content about endless battle between the two rivals is a house cat called Tom and a mouse called Jerry. Often Tom rarely succeeds in catching Jerry by Jerry mouse too smart, swift and lucky. Yet during the chase, Tom and Jerry has developed a close relationship which is less seen in other animated series. Although the contents of the Tom and Jerry could see the scenes of violence, it has still made up such wonderful childhood for many children all over the world. Tom & Jerry is really impressive. First, it’ll introduce children to classical music. Second, it’ll give them an appreciation for cartoons made at an earlier time. Third, since Tom always provokes the fights, and yet since Jerry usually outsmarts Tom, kids are taught that the one who provokes fights will usually lose. Last, but certainly not least, it’s entertaining. School-age children will enjoy this.