MATHEMATICS PAPER 2 GRADE 12 NSC EXAMS PAST PAPERS AND MEMOS JUNE 2019
MEMORANDUM QUESTION 1
1.1
Mean = 48
✔ 48 (1)
1.2
SD/SA = 22,08 Penalty of 1 mark for incorrect rounding
✔✔22,08 (2)
1.3
Girls performed better. The girls’ mean percentage is bigger than that of boys and the girls standard deviation is smaller than that of boys
✔Girls ✔Reason (2)
1.4
51 – 48 = 3 ∴each boy’s percentage must be increased by 3.
✔3 (1)
1.5
Boys’ standard deviation will remain the same
✔remain the same (1)
[7]
QUESTION 2
2.1
Ages (in years) Frequency Cumulative Frequency 18 ≤ x < 28 4 4 28 ≤ x < 38 10 14 38 ≤ x < 48 14 28 48 ≤ x < 58 17 45 58 ≤ x < 68 12 57 68 ≤ x < 78 3 60
✔frequency ✔cumulative frequency (2)
2.2
✔grounding at (0 ; 18) ✔upper limits ✔shape (3)
2.3
48 ≤ x < 58
✔answer (1)
2.4
60 – 49 = 11 senior citizens
✔49 ✔answer(2)
2.5
Q1 = 39 Q2 = 50 Q3 = 58
✔value of Q1 ✔value of Q2 ✔value of Q3 (3)
2.6
✔minimum and maximum ✔ box (2)
[13]
QUESTION 3
3.1.1
✔substitution ✔answer (2)
3.1.2
mKM = y2 - y1 x2 - x1 = -4 - 7 7 - 0 = - 11 7 ✔substitution ✔gradient of KM (2)
3.1.3
mLM = y2 - y1 x2 - x1 = -4 - 2 7 - 10 = 2 tan α = 2 ∴ α = 63,43º
✔gradient of LM ✔ tan α = 2 ✔value of α (3)
3.1.4
tanθ = - 11 7 Ref ∠ = 57,53º ∴θ = 122,47º LMK = 122,47º - 63,43º = 59,04º
✔tanθ = - 11 7 ✔reference angle ✔value of θ ✔value of LMK∧ (4)
3.2
✔ y = 2x + 7 ✔ y = -x - 1 2 2 ✔value of x ✔value of y
OR
✔mKL = -5 10 ✔mNM = -5 10 ✔value of x ✔value of y
OR ✔Midpoint of KM = ✔ Midpoint of LN = ✔value of x ✔value of y (4)
3.3
mLM × mMN = 2 × (-½) = -1 ∴LMN = 90º
OR LMN is a right angle
✔product of gradients ✔conclusion (2)
3.4
LMN = 90º and LMK = 59,04º ∴KMN = 90º - 56,04º = 30,96º Area of KMN = ½ × √170 × 5√5 × sin30,96º =37,50 square units
✔KL = NM = 5√5 ✔KM = √170 ✔LMN = 90º and LMK = 59,04º ✔KMN = 30,96º ✔Area of KMN Δ (5)
[22]
QUESTION 4
4.1
M (2 ; 4)
✔value of x ✔value of y (2)
4.2
r2 = (5 - 2)2 + (0 - 4)2 = 25 ∴ (x - 2)2 + (y - 4)2 = 25
✔ (x - 2)2 ✔ (y - 4)2 ✔25 (3)
4.3
mGH = 8 - 0 -1 - 5 = - 8 = - 4 6 3 mtan = 3 /4 y - 8 = 3 /4 (x - 1) ∴y = 3 /4 x + 35 /4
✔mGH ✔mtan ✔substitution ✔equation (4)
4.4
At J, y = 0 (x - 2)2 + (0 - 4)2 = =25 (x - 2)2 = 9 x - 2 = ±3 x = 5 or x = -1 ∴ J (-1;0)
✔ y = 0 ✔substitution ✔ x = – 1 (3)
4.5
HJG is a right angled triangle (8,6 and 10). So the rotation of J around M will complete a rectangle Hence, j ((-1 + 6; 0 + 8)) = J'(5;8)
✔value of x ✔value of y (2)
4.6
x2 + y2 - 12x - 2y + 17 = 0 x2 - 12x + y2 - 2y = -17 x2 - 12x + 36 + y2 - 2y + 1 = -17 + 36 + 1 (x - 6)2 + (y - 1)2 = 20 Distance between the centres: ∴ the centre lies on the original circle
✔completing the square✔factorisation: x ✔factorisation: y ✔distance formula ✔conclusion (5)
[19]
QUESTION 5
5.1.1
(2)
5.1.2
sin84º = sin2 × 42º = 2sin42ºcos42º
✔double angle ✔expansion ✔substitution (3)
5.1.3
sin3º = sin(45º - 42º = sin45ºcos42º - -cos45ºsin42º
✔3° = 45° – 42° ✔expansion ✔substitution ✔substitution (4)
5.2
sin(x - 450º).tan(180º + x).sin(90º - x) cos(-x)-cos x.tan x.cos x cos x-cos x.sin x cos x -sin x
✔− cos x ✔ tan x ✔cos x ✔cos x ✔ sin x cos x ✔answer (6)
5.3.1
cos (A + B) = cos A cos B - sin A sin B
✔expansion (1)
5.3.2
✔compound angle identity ✔cos double angle identity ✔sin double angle identity ✔ (1 - cos2 α) (4)
5.4
✔ ✔ cos2 θ = cos2 θ - sin2 θ ✔substitution ✔standard form ✔values of p
OR
✔ 2cos2 θ − 1 ✔✔substitution ✔standard form✔values of p
OR
✔ ✔ 1 - 2sin2 θ ✔substitution ✔standard form ✔values of p (5)
[25]
QUESTION 6
6.1
y∈[-1;1] OR -1 ≤ y ≤ 1
✔answer (1)
6.2
g: ✔asymptotes at -90° and 90° ✔x-intercepts ✔shape (3)
6.3
180°
✔180° (1)
6.4
x = – 45°
✔– 45° (1)
6.5
x∈[45º ; 90º) OR 45º ≤ x < 90º
✔critical values ✔notation (2)
6.6
h(x) =sin (x – 45°) + 1
✔h(x) =sin (x – 45°) + 1
(1)
[9]
QUESTION 7
7.1
InΔ KLN : tan w = h LN LN = h tan w
✔ LN = h (1) tan w
7.2
✔correct sine rule ✔substitution ✔isolating LM ✔answer (4)
7.3
LM = h sin(y + z) and tan w sin z h = 38m, w = 21º, y = 52º and z = 59 ∴LM = 38.sin(52º + 59º) tan21º sin59º = 107,82m
✔substitution ✔answer (2)
[7]
QUESTION 8
8.1
the centre of a circle
✔answer (1)
8.2.1
AC = 10 cm (line from centre ⊥ chord)
✔length of AC ✔Reason (2)
8.2.2
(x + 5)2 = 102 + x2 x2 + 10x + 25 = 100 + x2 10x = 75 ∴ x = 7,5cm ∴radius = 7,5cm +5cm = 12,5cm
✔radius = (x + 5) ✔applying Pythagoras theorem ✔value of x ✔length of radius (4)
[7]
QUESTION 9
9.1
interior opposite angle
✔answer (1)
9.2.1
R2 = Q2 = 41° (∠s in the same seg) P4 = Q1 = 41° (tan-chord theorem) T1 = P4 = 41° (∠s opp. = sides)/(∠e teenoor gelyke sye)
OR
T1 = R2 = 41° (tan – chord theorem)/(raaklyn-koord stelling)
✔Statement ✔Reason ✔Statement ✔Reason ✔Statement ✔Reason (6)
9.2.2(a)
T2 + 34° = 78° (tan - chord theorem ) ∴T2 = 44°
✔Statement ✔Reason (2)
9.2.2(b)
41° + Q2 + 44° + 34° = 180° ( opp. ∠ s of a cyclic quad.) ∴Q2 = 61°
✔Statement ✔Reason (2)
9.2.2(c)
T4 = 41° + 61° ( ext. ∠s of a cyclic quad.) ∴T4 = 102° OR T4 + 44° + 34° = 180° (int.∠s of a Δ)
✔Statement ✔Reason
OR
✔Statement ✔Reason (2)
9.2.2(d)
W + 41°+ 41° = 180° ( int .∠s of a Δ) ∴ ܹW = 98°
✔Statement ✔ Reason (2)
9.2.3(a)
Q2 = 61º and T2 = 44º ∴ Q2 ≠ T2 ∴ QR is not parallel to PT (alt. ∠s are not equal)
✔Q2 ≠ T2 ✔alt. ∠s are not equal (2)
9.2.3(b)
R2 + W = 41º + 98º = 139º ≠ 180º ∴ PRTW is not a cyclicquad. (Opp. ∠s are not supp.)
✔R2 +W ≠ 180º ✔ PRTWis not a cyclicquad. (2)
9.2.3(c)
R1 = T2 = 44°(∠s in same seg) R1 + R2 = 44° + 41° = 95° ≠ 90° ∴ TQ is not a diameter (∠subt. by TQ is not a right angle)
✔R1 + R2 ≠ 90º ✔TQ is not a diameter (2)
[21]
QUESTION 10
10.1
Construction: Draw heights h and l on KR and KS respectively. Join LS and MR Proof: But: area of ΔLRS = area of ΔMSR Area of ΔKRS = Area of ΔKRS Area of ΔLRS Area of ΔMSR ∴ KR = KS RL SM
✔construction ✔ratio of areas ✔ratio of areas ✔same base and same height ✔ Area of ΔKRS = Area of ΔKRS (5) Area of ΔLRS Area of ΔMSR
10.2.1
AB = 5 units
✔5 (1)
10.2.2(a)
C is common CBA = CFB (both =90°) CAB = CBF (sum of ∠s of Δ) ∴ ΔCBA|||ΔCFB (∠, ∠, ∠)
✔Statement / Reason ✔Statement / Reason ✔Reason (3)
10.2.2(b)
CB = CA (|||Δs) CF CB CB2 = CF.CA ∴ CF = CB 2 CA
✔proportion ✔reason ✔ CB2 = CF.CA (3)
10.2.3
CF = CB 2 CA CF = (12)2 13 ≈ 11units
✔substitution g ✔length of CF (2)
10.2.4
AF = 13 – 11 = 2 unit
✔length of AF (1)
10.2.5
CB = CA = (prop. theorem ; DF||BA ) BD AF 12 = 13 BD 2 ∴ BD = 24 13
CF = CB (prop. theorem ; DF ||BA ) FE BD 11 = 12 FE 24 13 ∴FE = 22 units 13
✔proportion ✔reason ✔length of BD ✔proportion ✔length of FE (5)
[20]
TOTAL: 150