TECHNICAL MATHEMATICS PAPER 2
GRADE 12
NATIONAL SENIOR CERTIFICATE
MEMORANDUM
SEPTEMBER 2018
NOTE:
Symbol | Explanation |
M | Method |
MA | Method with accuracy |
A | Accuracy |
CA | Consistent accuracy |
S | Simplification or Statement |
R | Reason |
QUESTION 1 | |||
1.1 | AB = √( x2 - x1)2 + ( y2 - y1)2 = √(0 + 2)2 + (3 - 0)2 = √4 + 9 ≈ 3, 61 | ✓MA formula & substitution ✓S Simplification ✓CA Answer in decimal format | (3) |
OR | |||
AB2 = OB2 + OA2 (Pyth) =22 + 32 = 4 + 9 AB =√13 ≈ 3, 61 | ✓MA Pythagoras ✓S Simplification ✓CA Answer in decimal format | (3) | |
1.2 | mAB = y2 - y1 x2 - x1 = 3 - 0 0 + 2 = 3/2 Equation of the line: y - y1 = m ( x - x1 ) y - 0 = 3/2 ( x + 2) y = 3/2 x + 3 | ✓MA formula & substitution ✓M Formula equation of line ✓A Substitute pt A or B ✓CA Answer in standard form | (4) |
1.3 | tanOBA = mBA tan OBA = 3/2 OBA = 56, 31° OAB= 90°- 56, 31°= 33, 69° | ✓A subst. into correct formula ✓CA value of OBA ✓CA value of OAB | (3) |
1.4 | Scalene triangle OR Right angled triangle | ✓A | (1) |
1.5 | a = 2 b = 3 Equation of ellipse x 2 + y 2 =1 4 9 | ✓A value of ✓A value of ✓CA Equation of ellipse | (3) |
[14] |
QUESTION 2 | ||
2.1 | r 2 = x2 + y2 | ✓M Calculating ✓CA Value of r ✓A x = 0 ✓CA y = – 10 (neg. value) (4) |
2.2 | Radius of smaller circle = 10 – 4 = 6 equation of smaller circle x2 + y2 = 36 | ✓M radius of smaller circle ✓CA Equation of smaller circle (2) |
2.3 | Bigger circle mradius= y2 - y1 x2- x1 = 6 - 0 -8 - 0 =- 3/4 mtangent = 4/3 equation of tangfent: y - y1 = m ( x - x1 ) y - 6 = 4/3( x + 8) y = 4/3 x + 32/3 + 6 3=4/3 x + 50/3 | ✓MA gradient of radius of bigger circle ✓CA Gradient of tangent ✓A Subst. A into equation ✓CA Standard form of equation (4) |
[10] |
QUESTION 3 | ||||
3.1 | 3.1.1 | x2 + y2 = r 2(Pyth) 52 + y2 = 6, 42 y = - √40, 96 - 25 =-√15, 96 = -3, 99... ≈-4 units | ✓A Pythagoras ✓A Substitution ✓CA Simplification ✓CA Rounded answer | (4) |
3.1.2 | cotθ- cos ecθ x sin2 θ = 5/-4 - 6,4/-4 x (-4/6,4) 2 = -5/4 + 6,4/4 x 16/40,96 = 5 | ✓CA cot θ ✓CA cosec θ ✓CA Sin θ ✓CA Simplification of sin2 θ ✓CA Answer | (5) | |
3.1.3 | cosθ = 5/6.4 θ = 360° - cos-1 (5/6.4) = 360° - 38, 624...° = 321, 4° | ✓A Ratio ✓CA Reference ∠ ✓A 4th Quadrant ✓CA Answer, rounded | (4) | |
3.2 | sin (180° + x) tan (360° + x)cos(180° - x) = (-sin x)(tan x)(-cos x) = (-sin x) sin x (-cos x) cos x = sin2x | ✓A sin x ✓A tan x ✓A -cos x ✓A sin x tan x ✓CA answer | (5) | |
3.3 | tan 2 5x | ✓A tan 2 5x | (1) | |
3.4 | 2 tan ( x - 23°) + 5 = 0 tan ( x - 23°) = -5/2 Ref ∠ = tan-1 (2,5) = 68,19...° x - 23° = 180° - 68,19...° OR 360°- 68,19...° x = 111,8...° + 23° OR 291,80...° + 23° = 134,8° or 314,8° | ✓A RHS = -2,5 ✓CA Ref ∠ ✓CA 2nd quadrant ✓CA 3rd quadrant ✓A Adding 23° by ✓CA Answers | (6) | |
[25] |
QUESTION 4 | |||
4.1 | In ∆AHC: AH =cosec24,5° HC AH= 100 sin24,5° ≈241 m | ✓A Ratio ✓A Substitution ✓CA Rounded answer | (3) |
4.2 | In ∆BHC: | ✓A Ratio ✓A Substitution ✓CA Rounded answer | (3) |
4.3 | AB2 = AC 2 + BC 2 - 2AC x BC cos ACB = 2192 + 2612 - 2´ 219´ 261´cos105° = 145669, 6756 AB = 381, 6669... ≈ 382 m | ✓A cos rule | (4) |
4.4 | Area DABC = 1 ab sin C2 = 1 ´ 261´ 219 ´sin105° 2 = 3000847, 5 » 3 000 848 m2 | ✓A Area rule ✓CA Substitution ✓CA value of Area | (3) |
[13] |
QUESTION 5 | |||
5.1 | Period = 360° = 180° 2 | ✓A Answer | (1) |
5.2 | A(45°; 0) & C(225°; 0) | ✓A A(45°; 0) ✓A C(225°; 0) | (2) |
5.3 | 90° < x < 180° | ✓A End points | (2) |
5.4 | 45° < x < 165° and/en 225° < x < 285° | ✓A✓ A first ✓A✓ A second | (4) |
5.5 | y ∈ [-3;3] or - 3 ≤ y ≤ 3 | ✓A critical values ✓A notation | (2) |
[11] |
QUESTION 6 | ||||
6.1 | SupplementaryOR Add up to 180° | completed | (1) | |
6.2 | ||||
6.2.1 | E = 90° (∠ in semi-circle) | ✓S ✓R | (2) | |
6.2.2 | BDE = 45° (co-int∠s ;BE//GD) | ✓S ✓R | (2) | |
6.2.3 | BE = ED = 8 cm (sides opp. = angles) | ✓S ✓R | (2) | |
6.2.4 | BGD = 90° (∠ in semi-circle) BGDE is a rectangle (All Ðs = 90°) BGDE is a square (diagonals bisect at 45°) GD = 8 cm (all sides=) | ✓SR ✓SR ✓SR ✓S | (4) | |
6.3 | ||||
6.3.1 | S1 = 41° (alt ∠s ; TS // WQ) | ✓S ✓R | (2) | |
6.3.2 | V = 139° (opp ∠s of cyclic quad) | ✓S ✓R | (2) | |
6.3.3 | S2 = 64° (tan-chord) | ✓S ✓R | (2) | |
[17] |
QUESTION 7 | ||||
7.1 | Divides the other two sides proportionally | ✓ completed statement | (1) | |
7.2 | 7.2.1 | Let QC = x. QC = QM (prop th; MC // PN) CN MP x = 3 2,86 2 x = 3 x 2,86 2 = 4, 3 cm | ✓ S ✓R Proportionality ✓S Set up proportion ✓S Simplification ✓S Answer | (5) |
7.2.2 | Let NR = y. QN = QM (prop th/ewer. st; MN // PR) NR MP 7,15 = 3 y 2 y = 2 x 7,15 3 = 4,8 cm | ✓R Proportionality MN // PR ✓S Set up proportion ✓S Simplification ✓S Answer | (4) | |
7.3 | ||||
7.3.1 | Bˆ is common BDE = 90° = A DBDE /// DBAC (AAA) | ✓S ✓S ✓R | (3) | |
7.3.2 | BE = 502 +1002 (Pyth) ≈112 cm Let AE = x cm BD = DE (/// Δs) BA AC 100 = 50 x +112 80 x +112 = 80 x100 50 x = 48 cm | ✓S BE = 112 ✓S Proportionality ✓S setup proportion ✓S value of AE | (4) | |
7.3.3 | Area DBDE = ½ x DE x DB | ✓S formulae ✓S substitution ✓S value of ratio | (3) | |
7.3.4 | Area AEDC = Area ABC – Area DBE = 6400 – 2500 = 3900 cm2 | ✓MA ✓CA value of area | (2) | |
[22] |
QUESTION 8 | ||||
8.1 | ||||
8.1.1 | reflex CAE = 2/3 x 360° = 240° | ✓A Multiply by 2/3 x 360° | (1) | |
8.1.2 | obtuse CAE = 360° - 240° = 120°CAB = 60° | ✓S ✓S | (2) | |
8.1.3 | d = s = rθ = 50 x 240° x π 180 = 200π 3 ≈ 209 cm | ✓A Formula ✓A Multiply 180° ✓A Substitution ✓CA Answer ✓CA Rounding | (5) | |
8.1.4 | ACP = 90° (tan ⊥ radius) G = 90°(corrsp ∠s; BG || CP) GB = sin 60° 80 GB = √3 x 80 2 = 40√3 ≈69 cm CP = GB = 69 cm | ✓A G = 90° Ratio ✓A Ratio ✓CA Simplification ✓CA Answer ✓A CP = GB | (5) | |
OR GA = AC – BP (opp sides of rectangle) = 50 – 10 = 40 cm GB » 69 cm (Pyth) CP = GB = 69 cm | OR ✓A G = 90° Ratio ✓A GA = 40 cm ✓CA Pythagoras ✓CA Answer ✓A CP = GB | (5) | ||
8.1.5 | Length of belt = CH + HF + FP + CP = 209 +69 + 21 + 69 = 368 cm | ✓A HF = CP ✓CA Answer | (2) | |
8.2 | d = 19 x = 13 4h2 - 4dh + x2= 0 4h2 - 4 (19) h +132 = 0 4h2 - 76h +169 = 0 h = -b ± √b2 - 4ac 2a = 76 ± √(-76)2 - 4 (4)(169) 2(4) = 76 ± √3072 8 3 cm and 16 cm | ✓A Formula ✓A Substitusie ✓M Standard form ✓A Quadratic formula ✓CA Subsitutisie ✓CA Answers ✓A Rounding | (7) | |
[22] |
QUESTION 9 | ||||
9.1 | 9.1.1 | w = 2πn | ✓A Formula | (3) |
9.1.2 | D = 40 cm = 0, 4 m | ✓A Convert to m | (4) | |
9.2 | Vrectangluar = l x b x h | ✓A Subst. into formula | (5) | |
[12] |
QUESTION 10 | ||
Ar = a(o1 + on + o2 + o3 + o4 + ... + on-1) 2 = 5(8 + 3 + 10 + 9 + 9 +4) 2 = 187.5cm2 OR AT = a(m1 + m2 + m3 + ... + mn) = 5(8 + 10 + 10 + 9 + 9 + 9 + 9 + 4 + 4 + 3) 2 2 2 2 2 = 187.5cm2 | 🗸formula 🗸value of a 🗸substitution 🗸Area OR 🗸formula 🗸value of a 🗸substitution 🗸Area | (4) |
TOTAL | 150 |