Triangle: 3 =

Because EFGH is square. According to the nature of the square, EH is parallel to FG, so we can know that angle MNH=90 degrees and angle HMN= angle b.

Because in triangle ABC, AC=BC=6 and angle C=90 degrees, the triangle is an isosceles right triangle. So the angle B=45 degrees.

Therefore, angle HMN= angle B=45 degrees. And because the angle MNH=90 degrees; So: triangle HMN is an isosceles right triangle.

[2] waist circumference: CF= movement distance = T. So GB = 6-3-t = 3-t.

GN=GB=3-t，HG=3

HN=HG-GN=3-(3-t)=t

So the waist length of an isosceles triangle is t.

(3) When 0

When 3 =

I hope it helps you&; Adopted ~ thank you!