MATHEMATICS PAPER 2 GRADE 12 NATIONAL SENIOR CERTIFICATE MEMORANDUM NOVEMBER 2020
NOTE:
If a candidate answers a question TWICE, only mark the FIRST attempt.
If a candidate has crossed out an attempt of a question and not redone the question, mark the crossed out version.
Consistent accuracy applies in ALL aspects of the marking memorandum. Stop marking at the second calculation error.
Assuming answers/values in order to solve a problem is NOT acceptable.
GEOMETRY
S A mark for a correct statement (A statement mark is independent of a reason)
R A mark for the correct reason (A reason mark may only be awarded if the statement is correct)
S/R Award a mark if statement AND reason are both correct
QUESTION 1
1.1
a = 9,5 b = 0,909.. = 0,91 y = 9,5 + 0,91x
a = 9,5 b = 0,91 equation (3)
1.2
correct slope going through 2 points: (50 ; 55) or (40 ; 46) or (60 ; 64) or (0 ; 9,5) or (45 ; 50) (2)
1.3
Final exam mark ≈72,22%(calculator) OR y = 9,5 + 0,91(69) ≈72,29%
answer(2) substitution answer (2)
1.4
r = 0,95
? answer(A) (1)
1.5
There is a very strong positive correlation between the Mathematics and Physical Sciences mark.
? strong(1)
1.6
The teacher concludes that the higher the learners' Mathematics marks, the higher the learners' Physical Sciences marks.
answer (1)
[10]
QUESTION2
2 018
2 175
2 182
2 215
2 254
2 263
2 267
2 271
2 293
2 323
2 334
2 346
2.1
July
? answer
2.2
x= 26 941 Answer only: Full marks 12 = 2 245,083.. ≈ 2 245,08 aircraft landings
? 26 941 ? answer
2.3
Standard deviation for landings at the King Shaka International airport: s = 86,30
?? answer
2.4
(x - σ ; x + σ) = (2 245,08 – 86,30 ; 2 245,08 + 86,30) limit = (2 158,78 ; 2 331,38) There were 9 months when the aircraft arrivals at the King Shaka International airport were within one standard deviation of the mean.
? x - σ ? x + σ ? answer
2.5
The standard deviation of the number of landings at the Port Elizabeth Airport will be higher than the standard deviation of the number of arrivals at the King Shaka International Airport OR C.
? answer
[9]
QUESTION3
3.1
mWP= 4 - (-4) = 8 - 4 - 0 - 4 mWP = -2
? substitution of W and P ? mWP (2)
3.2
mST= ½ (given) (mWP)(mST ) = (- 2)(½) = -1 ST ⊥ WP
? (mWP)(mST) ? (mWP)(mST) = -1
3.3
5y + 2x + 60 = 0 y = - 2/5x -12 -2/5x-12 = ½x + 6 - 4x -120 = 5x + 60 9x = -180 x = -20 y = - 2/5 (- 20)-12 y = -4 S(–20; –4) OR
? mSK ? size of b ? size of NMS ? method ? answer (5)
3.6
In ΔSRW: ⊥h= –4 – (–20) ⊥h= 16units Area DSRW = ½(⊥h)(WR ) =½(16)( 72/5) =115,2square units Area SWRL = 2Area ΔSRW =2(115,2) = 230,4square units
OR In DSRW: ⊥h = –4 – (–20) ⊥h= 16units Area SWRL =16 x 72/5 = 230,40 square units
OR SW = √(- 20 + 4)2 +(- 4 - 4)2 = 8√5 = 17,89 SR = √(- 20 + 4)2 +(- 4 + 102/5)2 =16√29 = 17,2 5 Area SWRL = 2 x Area ΔSRW = 2(½SW x SR sinθ) =2(½8√5 x 16√29 sin 48,37°) 5 =230,41square units
?⊥h ? substitution ? area Δ ? answer (4)
? ⊥h ? ? substitution ? answer (4)
?SW =8√5 ?SR =16√29 5 ?substitution ?answer (4)
[21]
QUESTION 4
4.1
x2 + y 2 = r 2 r2 = (- 3)2 + (4)2 = 25 x2 + y 2 = 25
O (0 ; 0 ) and M(–3; 4) mOM = 4 - 0 = - 4 OR 0 - 4 = - 4 - 3 - 0 3 0 - (-3) 3 mNM = 3 4 y - 4 = 3/4 (x - (-3)) OR y = 3/4x + c y - 4 =3/4x + 9 4 =3/4 (-3) + c y = 3/4x + 25 c = 25 y =3/4x + 25/4
? mOM = - 4/3 ? mNM = 3/4 ? substitution of m and M ? equation (4)
4.4
N(–11 ; p) y = 3/4x + 25/4 p =3/4(-11)+ 25/4 OR 4 - p = 3/4 - 3 - (-11) p =- 2 N(-11;- 2) - 3 + xS= 0 and 4 + yS= 0 2 2 S(3;- 4) SN =√(-11- 3)2 + (- 2 - (-4))2 = 10√2 units or 14,14 units
?subst x = –11 into eq or gradient ?p =- 2 ?xS ? yS ?answer (CA) (5)
4.5
B(- 2; 5) BM = √2 units Radius of circle centred at M = 8 units k = 8 - 2 or k = 8 + 2 = 6,59 units = 9,41 units = 6,6 units = 9,4 units
? 2
?? k = 6,6
?? k = 9,4 (5)
[19]
QUESTION 5
5.1
Period of g = 360°
? answer (1)
5.2
Amplitude of f =½
? answer (A) (1)
5.3
f (180°) – g(180°) = ½ - (-½) = 1
?1 (1)
5.4.1
x = 140,9°
? x = 140,9° (1)
5.4.2
3 sin x + cos x ≥ 1 √3 sin x +½cos x ≥ ½ 2 sin x cos 30° + cos x sin 30°≥ ½ sin(x + 30°) ≥ ½ sin(x + 30°) = ½ at x = 0° or x = 120° x ∈ [0°;120°] OR 0° ≤ x ≤120°
?dividing by 2 ?cos30°; sin 30° ?sin(x + 30°) ≥ ½ interval (4)
OR cos(90° +θ ) =a 6,5 - sinθ=a 6,5 - 12 =a ∴ a = -6 13 6,5 b = √(6,5)2 - (-6)2 = - 5/2
? sin(θ + 90°) =b 6,5 ? cosθ ? - 5 =b 13 6,5 ? value of b (4)
? cos(θ + 90°) =a 6,5 ? - sinθ ? value of a ? value of b (4)
6.2
sin 2x. cos(-x) + cos 2x. sin(360° - x) sin(180° + x) = sin 2x cos x + cos 2x( - sin x) - sin x = sin(2x - x) - sin x = sin x -sin x = -1
? cos(-x) = cos x
? sin(360° - x) = -sin x ?sin(180° + x) = -sin x ? numerator = sin x ? answer (5)
6.3
6 sin2x + 7 cos x - 3 = 0 6(1 - cos2x) + 7 cos x - 3 = 0 6 - 6 cos2x + 7 cos x - 3 = 0 6 cos2x - 7 cos x - 3 = 0 (3cos x + 1)(2 cos x - 3) = 0 cos x = - 1/3 or cos x = 3/2 (N/A) x = 109,47° + k.360°; k ∈Z or x = 250,53° + k.360°; k∈ Z
? identity ? standard form ? factors ? both solutions of cos x ? x = 109,47° & 250,53° ? + k.360°; k ∈Z (6)
6.4
x + 1/x = 3cos A (3cosA2) = (x + 1/x)2 9cos2A = x2 + 1 + 2 x2 9 cos 2 A = 2 + 2 cos 2 A = 4/9 cos 2A = 2 cos 2 A -1 = 2(4/9)- 1 = - 1/9
OR x2 - 2 + 1 = 0 x2 (x - 1/x)2= 0 x2 = 1 x = ±1
3cosA = 2 or 3cosA = -2 cosA = 2/3 or cosA = -2/3 cos2A = 2cos2A - 1 = 2(±2/3)2 - 1 = - 1/9
?squaring both sides ? 9cos2A = x2 + 1 + 2 x2 ?cos 2 A = 4/9 ? cos 2A= 2cos2 A-1 ? answer (5)
? x = ±1
? cos A =2/3 ? cos A = - 2/3 ?double angle identity ? answer (5)
[24]
QUESTION7
7.1
tan 30° = √3r QS QS= √3r tan 30° = √3r or √3r 1 √3 √3 3 = 3r
?? trig ratio ? QS subject (3)
7.2
Area of flower garden = π (3r )2 - πr2 = 9πr 2 - πr 2 = 8πr2
? substitution into difference of areas ? answer (2)
7.3
RS2 = r2 + (3r)2 - 2(r)(3r) cos 2x = r2 + 9r2 - 6r2 cos 2x = 10r2 - 6r2 cos 2x = r2(10 - 6 cos 2x) RS = r √10 - 6 cos 2x
?substitution into cosine rule correctly ?10r2 - 6r2 cos 2x ?r2(10 - 6 cos 2x) (3)
7.4
RS = 10√10 - 6 cos 2(56) = 34,9966... » 35 m
?substitution ? answer (2)
[10]
QUESTION8
8.1.1(a)
O2 = 64° [∠ at centre = 2 × ∠ at circumference]
? S ? R (2)
8.1.1(b)
M2 = 90° [Line from centre to midpt of chord] KON=90° + 26° = 116° [ext ∠ of D] O1 =116° - 64° =52°
OR M2 = 90° [Line from centre to midpt of chord] O3 = 64° [sum of ∠s in D] O1 = 52° [ ∠s on straight line]
? S ? R ? S ? answer (4)
? S ? R ? S ? answer (4)
8.1.2
PKO + P = 128° [sum of ∠s in ∆] PKO= P [ ∠s opp = sides] = 64° K2 = 32° orK2 = K1 KN bisects OKP
OR K2 = KNO [ ∠s opp = sides] K2 + KNO = 64° [sum of ∠s in ∆] K2 = 32° orK2 = K1 KN bisects OKP
? S ? S ? S (3)
? S ? S ? S (3)
8.2
8.2.1
F1 = D1 [tan chord theorem] D1 = B [Given] F1 = B FG || BC [corresp ∠s =]
? S ? R ? F1 = B ? R (4)
8.2.2
GC = FB [line || one side of Δ] AC AB x + 9 = 5 2x - 6 7 7x + 63 =10x - 30 3x = 93 x = 31
OR AG= 2x - 6 -(x + 9) = x -15 AG = AF [line || one side of Δ] GC FB x -15 = 2 x + 9 5 5x - 75 = 2x +18 3x = 93 x = 31
OR AF = AG [line || one side of Δ] AB AC 2 = x - 15 7 2x - 6 7x - 105 = 4x -12 3x = 93 x = 31
? S ? R ? substitution ? answer (4)
? S ? R ? substitution ? answer (4
? S ? R ? substitution ? answer (4)
QUESTION9
9.1
Construction: Draw diameter KS and draw KR QST = 90° - TSK [radius ^ tangent] SRK = 90° [∠ in semi circle] SRT = 90° - KRT TSˆK = TRK [∠s same segment] QST = R
construction S/R S/R S S/R (5)
OR
9.1
Construction: Draw radii OS and OT QST = 90° - OST [radius ⊥ tangent] OST = STO [∠s opp = sides] SOT =180° - 2OST [∠s of D] R = 90° - OST [∠ at centre = 2 × ∠ circumf] QST = Rˆ
construction S/R S/R S S/R (5)
OR
9.1
Construction: Draw diameter KS and join K to T. QST = 90° - TSK [radius ⊥ tangent] STK = 90° [∠ in semi circle] K = 90° - TSˆK QSˆT = K but Rˆ = K [∠s same segment] QST = Rˆ
construction S/R S/R S S/R (5)
OR
9.1
Construction: Draw radii OT, OR and OS OST = OTS [∠s opp = radii] Also: OTR = ORT and ORS = OSR 2x + 2 y + 2z = 180° [∠s ofΔ] x + y + z = 90° y + z = 90° - x OSQ = 90° [radius ⊥ tangent] TSQ = 90° - x TSQ = y + z = R
construction S/R S/R S S/R (5)
OR
Construction: Draw radii OT and OS, tangent QT OSˆQ = 90° [radius ⊥ tangent] TSQ = 90° - TSO TSO = STO [∠s opp = radii] TOS = 180° - 2TSˆO [∠s of D] R = 90° - TSO [∠ at centre = 2 × ∠ circum] TSQ = R
construction S/R S/R S S/R (5)
9.2
9.2.1(a)
N2 = x[alt ∠s; PR || NQ]
S R (2)
9.2.1(b)
Q2 = x[tan chord theorem] OR M2 = x [tan chord theorem] Q2 = x[∠s in same segment
S R (2) S/R (2)
9.2.2
MN = MS [QN || PR; Prop Th] NR SP N1 = N2 = x [given] P3 = x [∠s in same segment] P3 = Q2 [= x] SQ = PS [sides opp = ∠] MN = MS NR SQ
S R (6)
[15]
QUESTION 10
10.1.1
DBE = 90° [∠ in semi-circle] DMA = 90° [ AM ⊥ DE ] FBDM is a cyclic quadrilateral [converse opp ∠s cyclic quad]
OR DBE = 90° [∠ in semi-circle] M2 = DBE=90° FBDM is a cyclic quadrilateral [converse ext ∠ of cyclic quad]
S R (3)
S R (3)
10.1.2
B3 = D2 [tangent chord th] F1 = D2 [ext ∠ cyc quad] B3 = F1
OR B1 = E = x[tangent chord th] F1 = 90° - x [∠ sum in Δ] D2 = 90° - x [∠ sum in Δ] F1 = D2 B3 = D2 [tangent chord th] B3 = F1
OR B1 = E = x[tangent chord th] B3 = 90° - x [straight line] F1 = 90° - x[sum of ∠s Δ] B3 = F1
S R (4) F1 = 90° - x = D2
R (4)
S R (4)
10.1.3
In ∆CDB and ∆CBE C = C [common ∠] CBD = CEB [tangent chord th] CDB = CBE [∠ sum in D] ∆CDB ||| ∆CBE
OR In ∆CDB and ∆CBE CBD = CB [tangent chord th] C = C [common ∠] ∆CDB ||| ∆CBE [∠∠∠]
S S/R R (3)
S/R S R (3)
10.2.1
BC = DC [||| Δs] EC BC BC2 = EC x DC = 8 x 2 = 16 BC = 4
ratio substitution answer (3)
10.2.2
BC = DB [||| Δs] EC BE DB = 4 = 1 BE 8 2 BE = 2DB DB2 + BE2 = DE2 [Pyth theorem] DB2 + (2DB)2 = 36 5DB2 = 36 DB2 = 36 5 DB = 6 = 2,68 units √5
BE = 2DB substitution into Pyth theorem DB2 = 36 5 answer (4)