Given that both sides of a triangle are AB, a > b, find the length range of the center line CD on the third side

Given that both sides of a triangle are AB, a > b, find the length range of the center line CD on the third side

2A + b > CD midline > b
Let the third pass of the triangle be C, because the sum of the two sides of the triangle is greater than the third side, and the difference between the two sides is less than the third side, so a + b > C > a-b
Because a > b, let the length of central line CD be X
The midpoint D is a + (a + b) / 2 > x > A - (a + b) / 2 and B + (a-b) / 2 > x > b - (a-b) / 2
Two style simultaneous
2A + b > CD midline > b