2024年北师大版九年级下册数学同步学与练第三章圆专题14切线长定理、圆内接正多边形 （2个知识点6种题型）（解析版）.pdfVIP

1426

倍速学习三种方法

1.

2.

1.

2.

3.

4.

5.

6.

1.

2.

3.

4.Rr

1.

1

2

3

4

①

②

③

1ABACBDOPCDAB=5AC=3BD

2

ACAPO

AC=AP

BPBDO

BP=BD

BD=PB=AB﹣AP=5﹣3=2

2

2.

1

2

3

4

5

中心角半径R

α

O

边心距

中心r

1.

()

n.

2.

.

O4

(AOBE)

OABAB

OOCDEFACEBFDO6

AEF(CBD)O3

(3)O12

n1n2.

n

.

22022ïABCDEFAGDH⊙OBGBG

A15B30C15165D30150

OAOBOGAOB6090BOG

AOGAOB906030BG15165

OAOBOG

AOB6090

BOGAOGAOB906030

BG15165

C

BOG

1.

1PAPB⊙OCD⊙OEPCD12APB60

1PA

2COD

1CACEO

CACE

DEDBPAPB

PCDPD+CD+PCPD+PC+CA+BDPA+PB2PA12

PA6

2P60

PCE+PDE120

ACD+CDB360120240

CACEO

OCEOCAACD

ODECDB

OCE+ODEACD+CDB120

COD18012060

2ABBCCD⊙OEFGABCDOB6cmOC8cm

1BOC

2BE+CG

3⊙O

1OFBEBFCFCGOBFOBEOCFOCG

ABCD

ABC+BCD180

OBF+OCF90

BOC90

21BOC90

OB6cmOC8cm

BC10cm

BE+CGBC10cm

3BC⊙OF

OFBC

SOBCOFBCOBOCOF1068

OF4.8cm

2.

32022ABCO

D

ÐADB=12°

15

AOBOÐAOB=24°

AOBO

ÐAOB=2ÐADB=24°

360°

=15

24°

15

3.

4ABCDROR=6ABCD

ABCD

6232

OOE^BCEÐBOC=90°ÐOBC=45°