2.B I doubt whether there are any mistakes in the topic. If it is a square, solve the equation. If it is a rectangle, solve the quadratic function.
3.b group discussion
4. C: The length of the hypotenuse midline is half that of the hypotenuse, ∴AD=BD=CD, ∴ C = ∠ DAC, ∫∠BAE+∠bad = 90, ∠DAC+∞.
5.D
E is EG∑AC, E and B are perpendicular to AC, and EM and BN are at m and n respectively.
∫EG∨AC
∴△DEG∽△DAC，
∴eg/AC = de/ad = DG/DC = 1/2∴AC = 2eg∴eg/fc = BG/BC = 2/3∴BD/BC = 1/3∴em。
6. d .∫s△ade = s trapezoidal DBCE, ∴△ADE's area is half that of △ABC ∴ (AD/AB) × (AE/AC) =1/2 ∴ AB = ∴ AD makes AD =/.
7. 1/4∧2005
You can ask if you don't understand.