(1) PQ (2) () 2 PR = PR P : P = R : R (2) () = P = P R M = XM : = M : M (1) (2) = N = N X M 161 (1) (2) F F = F F F EF = F E

5 1 1 1.1 2 159 O O PQ RS OR P = PQ P O M MQ O (1) M P (2) P : P R : R () PR P 160 > M : = M : M X (1) N = N M // N X M (2) M 161 (1) E = 8 = 4 = = E = (2) : = 2 : = E = E F 5 F EF F E

5 1 159 (1) PQ (2) () 2 PR = PR P : P = R : R (2) () = P = P R 160 2 M = XM : = M : M (1) (2) = N = N X M 161 (1) 159 160 2 2 (2) F F = F F F EF = F E F E 2

5 1 159 (1) O PQ 2 P = Q P P = PQ M PQ PQ O R O PMQ = 90 MQ PMQ M P Q (2) PQ O MQ P : P = P : 2 P sin 60 = 1 : 1 = : 1 OP = r O = 1 O = OP = r R : R = (O OR) : (OR O) = ( r r) : = : 1 ( r r ) S () (2) R : R = P : P(= : 1) P P = P P P = P R : R = P : P RP // { PR = P R M P O S PR = P Q PR = PR PR P 2

5 1 160 (1) M : M = : = : N M // N 1 (2) 1 { MX = N M = N N X M = N N N = N MX = M M 2 161 (1) 2 : = : 8 : = 4 : = 6 8 E 2 : = E : E 4 E 8 : 6 = (7 + E) : E 6(7 + E) = 8E E = 21 E = + E = + 21 = 24 (2) F 2 F : F = : = 1 : F = F = 5 = 15 = = 5 + 15 = 20 E 2 E : E = : = 2 : EF = 4 5 = 9 20 20 = 9 2 1 F 2 E

5 1 1.2 162 (1) 1 2 : 1 (2) I I P = 5 = 6 = P = I : IP = : 16 O H O O OE E OH G G O H (1) H = E (2) G 164 H K L M (1) K ( ) K LKM (2) H KLM () H KLM

5 1 5 G G 2 : 1 I 2 I O 2 O 2 1 G H I I I 1 2 2 I I I O I H 162 (1) 1 1 2 (2) 16 164 (1) (2) () KLM

5 1 162 (1) L M N MN // 2MN = M N G G : GM = : MN = 2 : 1 M L G G : G M = : LM = 2 : 1 G G M 2 : 1 2 1 G G : GM = 2 : 1 G : GN = G : GL = 2 : 1 G 2 : 1 (2) P 2 P : P = : = 5 : P = 5 8 = 5 8 6 = 15 4 I 2 I : IP = : P = 5 : 15 4 = 4 : 16 (1) H H // H H // H H H = 5 5 G M L M G 6 G O E P I H N

5 1 (2) EO E 1 : 2 OE = 1 2 HG EOG G : GE = H : OE = H : 1 2 = H : 1 2 H = 2 : 1 G E 2 : 1 164 (1) K L M L = M 1 ( i ) M HM = HK = 90 2 M K H H MKH = MH 2 2 L K H LH = LKH 1 2 MKH = LKH (ii) 2 L K L KL = L 2 M K KM = M 1 KL = KM (iii) = 90 L M H KL = KM (= 0 ) K H K L M ( i ) (ii) (iii) K LKM 2 (2) L M (1) L M KLM LMK 2 H KLM () LH = MH = 90 2 L M H HLM = HM L = K = 90 2 L K LK = K HM = K LK = MLH LH KLM 2 HM KML 2 K HK MKL 2 H KLM K

5 1 1. 165 Q Q R R S (1) S : S (2) R : RS 166 O O 2 : M OM = OM S 1 M S 2 S 1 S 2 = 167 1 9 = 4 E = 6 E E F F G G 168 P Q R P Q R 1 T R : R = 2 : 1 P : P = t : (1 t) 0 < t < 1 (1) Q Q t (2) t = 1 : RT 4

5 1 165 l l P Q R R R Q R P P Q = 1 ( ) Q P P Q R 1 ( ) P Q R 166 165 167 P Q R P Q R 1 R R R P P Q = 1 ( ) Q P P Q R ( ) P Q R 1 168 167 (2) T T T Q

5 1 165 (1) S S Q QR R = 1 S S 2 1 1 1 = 1 S : S = 1 : 2 (2) (1) S : = 1 : (1 + 2) = 1 : R RS S Q Q = 1 R RS 1 1 1 = 1 R : RS = : 1 166 M M O O = 1 1 1 2 5 = 1 = 5 2 : = 5 : 2 OM M O = 1 OM M 2 7 2 = 1 OM : M = 7 : OM = M S 1 = OM M S 2 M M = OM M M M = 7 1 1 = 7 1 2 Q Q 1 1 2 1 R R S S S 1 O 1 M 1 S 2 5 2

5 1 167 G G E E = 1 4 5 G G 6 = 1 G G = 5 2 G : G = 5 : 2 G = 9 2 7 = 18 7 168 (1) Q Q R R P P = 1 Q Q 2 1 t 1 t = 1 Q Q = 1 t 2t (2) t = 1 4 P : P = t : (1 t) = 1 ( 4 : 1 1 ) = 1 : 4 1 5 R t 4 9 2 T P 6 F G 1 t E Q Q : Q = (1 t) : 2t = : 2 T : T = P : P = 1 : (= 2 : 6) T : T = R : R = 1 : 2 (= : 6) T : T : T = 2 : : 6 T = 2 1 P 2 + + 6 = 2 11 1 R T 2 2 Q RT = 1 T : RT = : 1 2 = : 2 11

5 2 2 2.1 169 E ( ( ( ( E E ( 2 4 5 O O = E = O E 170 L M N H (1) LHN = (2) 4 L M N H 171 : : = 5 : : 1 O O O O O EF EF O E (1) (2) E = F 172 l O l P O P = 115 = P = P O l

5 2 169 O 1 1 O P P P O 1 P = 1 2 O 170 P Q 4 P Q P Q P = Q 4 P Q 171 172

5 2 169 ( ( ( ( ( : : : E : E = 1 : 2 : : 4 : 5 O = θ O = 2θ, O = θ, OE = 4θ, EO = 5θ θ + 2θ + θ + 4θ + 5θ = 60 O = θ = 24 E = 1 2 O = 1 (θ + 2θ + θ) 2 = 72 θ 2θ 5θ θ O 4θ E 170 (1) H = 90 H LH = L LH = LH 1 H = 90 H NH = N NH = NH 2 1 2 LHN = (2) MN // L MN = 1 = L 2 MNL L L = LMN (1) M H LMN = LHN 4 L M N H H N N

5 2 171 (1) = θ = 5θ = θ 5θ + θ + θ = 180 θ = 20 ( O = 2 = 2 20 = 40 O O = O = 180 40 = 70 2 2θ O θ (2) ( E E = E 1 ( F F = EF 2 // EF E = EF 1 2 E = F E O F 172 O = 90 P = P = 115 90 = 25 O = P = 25 115 P = 180 P = 180 115 25 = 40 P l

5 2 2.2 17 O G O G E F < 90 E F 4 G, E,, G = = 90 E = 1 4 G F E EF = 2 G O G = GF G = GF = 90 G GF G = GF 1 2 E = EF = 180 E F 174 S 6 E F S l S 2 E E S l F (1) S E F (2) F E () EF = E F

5 2 17 180 1 174 (1) (2) 2 ( i ) (ii) 2 (iii) 2 (iii) () EF E

5 2 17 G = GE = 90 G E G E = G 1 4 G F E EF = GF 2 G O G + G = 180 G = 180 G = GF G = GF = 90 G GF G = GF 1 2 E = G = GF = EF EF = 180 E F O E F G

5 2 174 (1) S E F l (2) F = F F = E F = E 1 E E + = 180 E = 180 = F 2 1 2 F E 2 E F E () F EF F 2 F EF (2) EF E EF : F = E : EF = E F F l

5 2 2. 175 2 O 1 O P O O (1) (2) P 175 2 l l R R r l O O O O d d r l = d 2 (R r) 2 l = d 2 (R + r) 2

5 2 175 (1) O O H OO H OH = O H = O O = 2 1 = 1 OO = OP + PO = 2 + 1 = = HO = OO 2 OH 2 = 2 1 2 = 2 2 O 1 1 H J I 2 1 (2) P I PI O H J O PJ O OH 1 : P 1 O PJ = 1 OH = 1 P PI = PJ + JI = 1 + 1 = 4 1 2 PI = 1 2 2 2 4 = 4 2

5 2 2.4 176,, T T = T 2 177 2 : 1 : 5 E 4 E : 178 = 10 = 9 = 8 E (1) E (2) E E

5 2 P 2 P P P ( i ) (ii) (iii) P P P T ( i ) P P = P P (ii) P P = P P (iii) P P = PT 2 176 (iii) 177 (ii) 178 (1) ( i ) (2) E E E

5 2 176 T T = T T T : T = T : = T 2 177 = E 2 = 8 2 = 9 16 2 = 4 : = : 4 2 1 E T 5

5 2 178 (1) E = 2 : = : = 10 : 8 = 5 : 4 = 5 9 = 5, = 4 9 = 4 E = 5 4 = 20 (2) = θ E 2θ + E = 180 : E = : E { } { } 1 2 10 8 sin 2θ : 1 2 E E sin (180 2θ) = : E 80 : (E E) = : E (1) E = 20 E E = 80 E = 80 20 2 10 θ θ 8 = x (> 0) cos θ = 2 + 2 2 2 = 75 + x2 1 20x = 102 + x 2 5 2 2 10 x 9 E cos θ = 2 + 2 2 = 82 + x 2 4 2 2 2 8 x = 48 + x2 16x 2 1 2 75 + x 2 20x = 48 + x2 16x 4(75 + x 2 ) = 5(48 + x 2 ) 2 = x 2 = 60 E E = 80 20 60 = 80

5.1 179 2 P Q l 1 Q P Q α l β P γ sin γ = sin α sin β α β γ 179 2 P Q α P Q l X P Q XY l XZ l XY XZ YXZ Q P Z α X Y l P l l P l P ( i ) P l l (ii) P l l P (iii) l l P l

5 179 P l l = α = 90 = sin α 1 = β = 90 = sin β 2 = γ = 90 = sin γ 1 2 sin γ = = sin α sin β = sin α sin β Q P α β γ l

5.2 180 (1) 1 (2) a 181 1 1 M O O E F F OM O OF (1) OM x (2) l l 2 () α β 1 2 O α β G H θ = GOH sin θ 2

5 2 1 2 5 180 (1) 4 (2) 2 181

5 180 (1) 1 P Q R S T U PQR PQR 2 : 1 PQR ( ) 1 1 = 1 2 8 PSU QST QRT 1 4 1 8 = 1 2 P S U R Q T

5 (2) E F F a H a 2 H = E 2 a E 1 2 a2 H = 6 a V 2 2 F V = 2 6 a = a r V = 1 r 8 2 a = 1 1 2 a2 sin 60 r 8 6 r = 6 a R F FE F F E H R H 2 R = 2 a 181 (1) ( 1 x 2 + x 1 ) ( 2 ) 2 = M 2 2 2 2x 2 x 1 2 = 0 x 2 G OM = x = 1 + 5 4 F θ O x 1 (2) l O H 2 ( ) l 2 = x 2 + 1 2 5 + 5 = 2 8 E () 2 α 2 β sin θ 2 = G O = 1 2 1 x = 6 4 15 = 5 + 1 6 a F H