volume one

I. Multiple choice questions/kloc-0 1.C2.C3.C4.A5.B6.B

Fill in the blanks. Tangency 8. 9. Tangent 10.2 or 8.

1 1. 12.

Third, answer questions.

13. solution: the distance from the center of point a to the straight line BC is

,

∴ When the radius is r = 3 and r < D, the straight line BC is out of the circle;

When the radius r = 4 = d, the straight line BC is tangent to the circle;

When the radius r = 5 >; D, the straight line BC intersects the circle.

14. The radii of the two circles are 5cm and 2cm respectively.

15. Proof: If AO and CO are connected, then ∠ACO =∠CAO, ∠ AOC = 2 ∠ B.

∵∠ACO + ∠CAO + ∠AOC = 180？ .

∴2∠CAO + 2∠B = 180？ . ∴∠CAO + ∠B = 90？ .

∠∠CAE =∠b，∴∠CAO+∠CAE = 90？ .

∴OA⊥AE is at point A.∴AE, O is tangent to point A.

16.( 1) Sketch.

(2) If ⊙O' and OB are tangent to point E and ⊙O is tangent to point G, then O, O' and point G are on the same straight line, and ∠O'OE = 45? .

Connection Ⅷ

∴ in Rt△O'OE,

Solution,

∴ The maximum cutting radius is10cm.

Volume b

First, multiple-choice questions 1. B 2。 A 3。 C

Fill in the blanks. Tangency is 5.45 or 135 6.5.

Third, answer questions.

7. Solve the equation and get.

When a straight line intersects a circle; When, the straight line is separated from the circle.

8. solution: AC = AF.

Proof: When connecting OO' and extending it, its extension line must pass through G point and connect O'F,

Then there is O'F⊥AB.

Let OA = R and the radius of ⊙O' be R.

In Rt△OFO.

That is to say, ∴.

∴ .

In Rt△AOC, OA = OC = R,

∴AC=，∴AC = AF。 Let O'E = r, then O'O = 4-r, O'E⊥OE.