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The answer to the second volume of the eighth grade math book 18.2 is urgent.
1. Yes

2. Yes. At this time, its four corners are right angles.

3. yes. At this time, it gets an equilateral quadrilateral with right angles.

4. Angle A=60 degrees, angle B=30 degrees.

5.( 1) angle BAD=60, angle ABC= 120.

(2)AB = 6 cm, AC = 10.39 cm.

6. We can know AB=CD by angle ABD= angle DBC= angle ADB, and AB=BC in the same way, so that AD is parallel to BC, and the quadrilateral ABCD is a diamond.

7.45 degrees

8. Rectangular. All four corners are right angles.

9.45 degrees.

10. Quadrilateral Amen Amen, EFCG are quadrilaterals with equal sides.

11.ab× DH = 2ao× od = 2aAbd area, and DH=2.4CM can be obtained.

12.B(- root number12,0), C (0 0,2), d (root number12,0)

13. The quadrilateral EFMN is a square.

14.3 species.

15.ADE are all equal to BAF.

16.BO = 2OD, which must be passed.

17. There are countless kinds. Just keep the two paths perpendicular to each other and cross the center of the square.