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Preparing for the Regents Examination Geometry, AK

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27 1. Common external tangents, −−−<br />

AG and −−−<br />

CM<br />

2. Radii −−−<br />

OA and −−−<br />

OC<br />

3. OAG and OCM are right angles.<br />

4. OAG and OCM are right triangles.<br />

5. −−−<br />

OA −−−<br />

OC<br />

6. Tangents −−−<br />

OM and −−−<br />

OG of circle P<br />

7. −−−<br />

OM −−−<br />

OG (Two tangent segments<br />

drawn from an<br />

external point are<br />

congruent.)<br />

8. OAG OCM (HL HL)<br />

9. −−−<br />

AG −−−<br />

CM (CPCTC)<br />

28 1. Circles A and B are congruent with<br />

tangent FG .<br />

2. −−<br />

AF is <strong>the</strong> radius of A. −−<br />

BG is <strong>the</strong> radius of<br />

B.<br />

3. −−<br />

AF −−<br />

BG<br />

4. AFC and BGC are right angles.<br />

5. FCA GCB<br />

6. FCA GCB (AAS AAS)<br />

7. −−<br />

AC −−<br />

BC<br />

29 mA 1 _ (<br />

2 CD BE ). 2(mA) <br />

mCOD mBOE. But mBOE mA.<br />

2(mA) mCOD mA. There<strong>for</strong>e,<br />

3(mA) mCOD.<br />

30 1. −−<br />

AB is tangent to O at E; −−−<br />

CD is tangent to<br />

O at F.<br />

2. −−<br />

OE OF<br />

3. −−−<br />

OA −−−<br />

OC ; −−<br />

OB −−−<br />

OD<br />

4. −−<br />

OE −−<br />

AB<br />

5. OEA and OEB are right angles.<br />

6. −−<br />

OF −−−<br />

CD<br />

7. OFC and OFD are right angles.<br />

8. OEA OFC (HL HL)<br />

OEB OFD<br />

9. −−<br />

AE −−<br />

EB (Addition<br />

−−<br />

CF −−<br />

FD postulate)<br />

or −−<br />

AB −−−<br />

CD<br />

13-5 Angles Formed by<br />

Tangents, Chords, and<br />

Secants<br />

(pages 368–371)<br />

1 (2) 96<br />

2 (1) 24<br />

3 (2) 144<br />

82 Chapter 13: <strong>Geometry</strong> of <strong>the</strong> Circle<br />

4 (4) 173<br />

5 (1) 38<br />

6 (1) 90<br />

7 a 40 b 62 c 225 d 45<br />

e 75 f 100 g 80 h 30<br />

8 a 79 b 38<br />

c x 50, y 60, z 120<br />

9 a 66 b 80 c 73<br />

d 130 e 33 f 73<br />

10 a 90 b 120 c 90 d 60<br />

e 30 f 60 g 30 h 90<br />

11 a 120 b 40 c 80<br />

d 40 e 140 f 100<br />

12 BC CD because in a regular hexagon,<br />

congruent chords subtend congruent arcs.<br />

Chords and a tangent that intercept congruent<br />

arcs are parallel. There<strong>for</strong>e, PC −−<br />

BD<br />

Note: Since <strong>the</strong>re are many variations of proofs,<br />

<strong>the</strong> following is simply one set of acceptable<br />

statements to complete each proof. Depending<br />

on <strong>the</strong> textbook used, <strong>the</strong> wording and <strong>for</strong>mat<br />

of reasons may differ, so <strong>the</strong>y have not been<br />

supplied <strong>for</strong> <strong>the</strong> method of congruence applied<br />

in each problem. (These solutions are intended<br />

to be used as a guide—o<strong>the</strong>r possible solutions<br />

may vary.)<br />

13 1. −−<br />

FB −−<br />

EC<br />

2. BEC EBF<br />

3. EHJ BHG<br />

4. EHJ BHG<br />

(Alternate interior angles<br />

are congruent.)<br />

5. BH _ <br />

HE<br />

HG _<br />

HJ<br />

(Corresponding sides<br />

of similar triangles are<br />

in proportion.)<br />

6. BH JH (The product of means<br />

HE HG equals <strong>the</strong> product of<br />

14 1.<br />

extremes.)<br />

−−<br />

BA −−−<br />

DA<br />

2. Diameter −−−<br />

DC<br />

3. BAD and DBC are right angles.<br />

4. −−<br />

AB is tangent to O at B.<br />

5. mDBA 1 _ m<br />

2 BD<br />

6. mDCB 1 _ m<br />

2 BD<br />

7. mDBA mDCB<br />

8. DBA DCB<br />

9. DBA DCB

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