If one side of the triangle is 5cm long and the other side is 7cm long, the value range of the middle line length on the third line is ()

If one side of the triangle is 5cm long and the other side is 7cm long, the value range of the middle line length on the third line is ()

This problem needs to be illustrated to understand
As shown in the figure, it is known that the lengths AC and ab of the two sides of the triangle are 5 and 7 respectively,
Extend ad to m, make ad = DM, connect cm
In △ abd and △ CDM,
AD=MD,
∠ ADB = ∠ MDC (equal to vertex angle),
BD = CD (properties of midline) & nbsp,
∴△ABD≌△CDM（SAS）,
∴CM=AB=7．
In △ ACM, 7-5 < 2ad < 7 + 5,
∴1＜AD＜6．
So the answer is: 1 < ad < 6