MATHEMATICS EXTENSION 2 2 August 2017 General Instructions • Reading time – 5 minutes • Working time – 3 hours • Write using black pen. • NESA approved calculators may be used. • Commence each new question in a new booklet. Write on both sides of the paper. • A reference sheet is provided. • In Question 11–16 show relevant mathematical reasoning and/or calculations • At the conclusion of the examination, bundle the booklets used in the correct order including your reference sheet within this paper and hand to examination supervisor. Total Marks: Section 1 – 10 marks (pages 3 - 6) 100 • Attempt Questions 1 – 10 • Allow about 15 minutes for this section Section 2 – 90 marks (pages 7 - 14) • Attempt Questions 11 – 16 • Allow about 2 hours and 45 minutes for this section NESA NUMBER: ........................ # BOOKLETS USED: . . . . . Marker’s use only. QUESTION 1-10 MARKS 10 11 12 13 14 15 16 Total 15 15 15 15 15 15 100 This task constitutes 40% of the HSC Course Assessment 1 2017 Mathematics Extension 2 HSC Trial Examination 3 Section I 10 marks Attempt Question 1 to 10 Allow approximately 15 minutes for this section Mark your answers on the answer grid provided (labelled as page 15). 1. The circle |z − 3 − 2i| = 2 is intersected exactly twice by the line given by: (A) Im(z) = 0 (B) |z − i| = |z + 1| (C) Re(z) = 5 (D) |z − 3 − 2i| = |z − 5| 2. If z1 + z2 + z3 = 0 and |z1 | = |z2 | = |z3 | = 1, then z12 + z22 + z32 equals: (A) −3 (B) − 1 3 (C) 0 (D) 3 3. The graph of y = ax2 1 has asymptotes at x = 5 and x = −3. + bx + c 1 Given the graph has only one stationary point with y-value of − , it follows that: 8 1 15 (A) a = , b = 1 and c = − 2 2 1 15 (B) a = , b = −1 and c = − 2 2 (C) a = 1, b = 2 and c = −15 (D) a = 1, b = −2 and c = −15 KILLARA HIGH SCHOOL 2 AUGUST 2017 4 2017 Mathematics Extension 2 HSC Trial Examination 4. √ 1 + sin x dx equals: √ (A) −2 1 − sin x + C (B) sin (C) cos x 2 x 2 + cos − sin x 2 x 2 +C +C √ (D) 2 1 − sin x + C 5. In how many ways can 30 distinct toys be divided into 10 packets? (A) 1030 (B) 3010 6. (C) 30! (3!)10 (D) 30! 10! × (3!)10 If ex + ey = 2 then dy is: dx (A) ex−y (B) −ex−y (C) ey−x (D) −ey−x 2 AUGUST 2017 KILLARA HIGH SCHOOL 2017 Mathematics Extension 2 HSC Trial Examination 7. 5 Consider the following shaded region on the Argand diagram. Which of the following inequations would represent the region? 8. (A) |z − 1 − i| ≤ 2 and π ≤ arg(z + 1) ≤ π 4 (B) |z + 1 + i| ≤ 2 and π ≤ arg(z + 1) ≤ π 4 (C) |z − 1 − i| ≤ 2 and 0 ≤ arg(z + 1) ≤ π 4 (D) |z + 1 + i| ≤ 2 and 0 ≤ arg(z + 1) ≤ π 4 x2 + y 2 = 1 are: The equations of the directrices of the ellipse 9 1 (A) x = ± √ 2 2 9 (B) x = ± √ 2 2 (C) x = ±3 √ 2 2 (D) x = ± 9 KILLARA HIGH SCHOOL 2 AUGUST 2017 6 9. 2017 Mathematics Extension 2 HSC Trial Examination The region bounded by the curves y = x2 and y = x3 in the first quadrant is rotated about the y-axis. Which integral could be used to find the volume of the solid of revolution formed? 1 1 1 3 2 (A) V = π y − y dy 0 1 1 1 y 2 − y 3 dy 1 2 y 3 − y dy 1 (B) V = π 0 (C) V = π 0 (D) V = π 0 x4 − x6 dx x2 y 2 + = 1 and a2 b2 the chord P Q subtends a right angle at (0,0). Which of the following is the correct expression? 10. The points P (a cos θ, b sin θ) and Q(a cos φ, b sin φ) lie on the ellipse (A) tan θ tan φ = − b2 a2 (B) tan θ tan φ = − a2 b2 (C) tan θ tan φ = b2 a2 (D) tan θ tan φ = − 2 AUGUST 2017 a2 b2 KILLARA HIGH SCHOOL 2017 Mathematics Extension 2 HSC Trial Examination 7 Section II 90 marks Attempt Questions 11 to 16 Allow approximately 2 hours and 45 minutes for this section. Write your answers in the writing booklets supplied. Additional writing booklets are available. Your responses should include relevant mathematical reasoning and/or calculations. Question 11 (15 Marks) sin x (a) Find dx cos3 x Use a SEPARATE writing booklet 2 (b) By splitting the integral find (c) Find x2 3x + 1 dx + 2x + 3 x tan−1 (x) dx 2 dx + x2 + x + 1 Find (e) Use the substitution t = tan x2 to find the exact value of 3 π 2 0 KILLARA HIGH SCHOOL 3 3 (d) x3 Marks 4 dx 5 + 4 cos x 2 AUGUST 2017 8 2017 Mathematics Extension 2 HSC Trial Examination Question 12 (15 Marks) Use a SEPARATE writing booklet Marks (a) If p2 = 24 − 70i, express p in the form a + bi, where a and b are real. (b) Given that p and q are real and also that 1 − 4i is a root of the equation: 2 x2 + (p + i)x + (q − 5i) = 0 (c) i. Find the values of p and q. 2 ii. Find the other root of the equation. 2 The complex number z = x + iy is such that z − 8i is purely imaginary. z−6 i. Find the locus of the point P representing z. 2 ii. Sketch the locus of x on an Argand diagram. 2 y (d) B β A α 0 x The diagram show the equilateral triangle OAB in the complex plane. O is the origin and the points A and B represent the complex numbers α and β respectively. π π + i sin . 3 3 −→ i. Write down the complex number BA. 1 ii. Show that α = μ(α − β). 2 iii. Prove that α2 + β 2 = αβ. 2 Let μ = cos 2 AUGUST 2017 KILLARA HIGH SCHOOL 2017 Mathematics Extension 2 HSC Trial Examination Question 13 (15 Marks) (a) 9 Use a SEPARATE writing booklet Marks Two tangents OA and OB are drawn from a point O to a given circle. Through A a chord AC is drawn parallel to the other tangent OB. OC meets the circle at E. Copy the diagram into your answer booklet (b) i. Prove that the triangles AF O and EF O are similar. 3 ii. Hence show that OF 2 = AF × EF . 1 iii. Hence prove that AE extended bisects OB. 2 Consider the function f (x) = (5 − x)(x + 1). On separate axes sketch, using 13 of a page, showing all important features, the graphs of: i. y = f (|x|) 1 f (x) 1 iii. y 2 = f (x) 1 ii. y = (c) 1 If x3 + 3mx + n = 0 has a double root, prove that n2 = −4m3 2 Question 13 continues on page 10 KILLARA HIGH SCHOOL 2 AUGUST 2017 10 2017 Mathematics Extension 2 HSC Trial Examination (d) 4 Use the method of cylindrical shells to calculate the volume of the solid formed when the area bounded by y = x and y = x2 is rotated about the line x = −1. 2 AUGUST 2017 KILLARA HIGH SCHOOL 2017 Mathematics Extension 2 HSC Trial Examination Question 14 (15 Marks) 11 Use a SEPARATE writing booklet Marks (a) Factorise P (x) = 2(x + 1)2 (2x + 1) + 1. 2 (b) Prove by mathematical induction that for all integer values of n, 3 tan−1 (c) π 1 1 1 1 + tan−1 + · · · + tan−1 2 = − tan−1 2 2 2×1 2×2 2n 4 2n + 1 Particles of mass m and 3m kilograms are connected by a light inextensible string which passes over a smooth fixed pulley. The string hangs vertically on each side, as shown in the diagram. The particles are released from rest and move under the influence of gravity. The air resistance on each particle is kv Newtons, when the speed of the particles is v ms−1 and the acceleration due to gravity is g ms−2 and is taken as positive throughout the question and is assumed to be constant. k is a positive constant. i. Draw diagrams to show the forces acting on each particle. 2 2 ii. Show that the equation of motion is: mg − kv 2m iii. Find the terminal velocity V or maximum speed of the system stating your answer in terms of m, g and k. ẍ = 1 iv. Prove that the time elapsed since the beginning of the motion is given by: 2m mg ln t= k mg − kv 3 v. If the bodies attain a velocity equal to half of the terminal speed, show by using the results in iii. and iv. that the time elapsed is V equal to ln 4, where V is the terminal velocity. g 2 KILLARA HIGH SCHOOL 2 AUGUST 2017 12 2017 Mathematics Extension 2 HSC Trial Examination Question 15 (15 Marks) Use a SEPARATE writing booklet (a) Given that In = xn e2x dx Marks xn e2x n − In−1 . 2 2 ii. Use the above result to find x2 e2x dx. i. Show that In = (b) 2 If α, β and γ are the roots of x3 + 5x2 − 2x − 3 = 0: i. Find α2 + β 2 + γ 2 . 1 ii. Find α3 + β 3 + γ 3 . 2 iii. Find the equation whose roots are (c) 3 1 1 1 , and . α β γ 2 As shown in the diagram below, a solid has parallel vertical ends and the base is horizontal. One end is a rectangle with length a and breadth b and the other end is a scalene triangle with base c and height d. The parallel ends are at a distance e apart. A typical slice is taken parallel to the ends at a distance x from the triangular end. i. Let the top of the trapezium be f , the base of the trapezium be g and the height of the trapezium be h. Show that: a−c x g =c+ e and hence write down similar expressions for both f and h in terms of x. ii. Hence find the volume of the solid. 2 AUGUST 2017 3 2 KILLARA HIGH SCHOOL 2017 Mathematics Extension 2 HSC Trial Examination Question 16 (15 Marks) (a) 13 Use a SEPARATE writing booklet The point P (a sec θ, b tan θ) lies on the hyperbola S are the foci. Marks x2 y 2 − = 1 and S and a2 b 2 The equations of the tangent and normal at P are as given below: x sec θ y tan θ − =1 a b by ax + = a2 + b2 Normal: sec θ tan θ Tangent: DO NOT PROVE THIS Copy the diagram into your writing booklet. The tangent at P intersects the x–axis at X and the y–axis at Y . PX i. Show that = sin2 θ PY ii. Deduce that if P is an extremity of a latus rectum, then PX e2 − 1 . = PY e2 3 1 Let the normal at P (a sec θ, b tan θ) intersect the y–axis at A. iii. Prove that ASY is right angled at S 2 iv. Explain why ∠P SA = ∠P S A 2 Question 16 continues on page 14 KILLARA HIGH SCHOOL 2 AUGUST 2017 14 (b) 2017 Mathematics Extension 2 HSC Trial Examination Newton’s method √ may be used to determine numerical approximations to 3 find the value of 2. This can be done by finding the real roots of the equation x3 − 2 = 0. Let x1 , x2 , x3 , . . . , xn , . . . be the series of estimators obtained by iterative applications of Newton’s method. i. Taking xn as the first root, use Newton’s method to show that: 2 1 xn+1 = xn + 3 (xn )2 1 ii. Show algebraically that: 2 xn+1 − iii. Given that xn > iv. Show that x12 √ 3 √ 3 2= xn − √ √ 2 3 2 2xn + 3 2 3(xn )2 2 show that: 2 √ √ 3 3 xn+1 − 2 < xn − 2 √ and 3 2 agree to at least 267 decimal places. 2 2 End of Examination 2 AUGUST 2017 KILLARA HIGH SCHOOL .*$)%$?(" (!$# +"*&"% >4 ?4 @4 /"#$*%$1$)%$"/%$ )%"+*%$$%)$%*,$/4 $1*)%"+*%$) -ݖଵ ' ݖଶ ' ݖଷ .ଶ * ݖଵଶ ' ݖଶଶ ' ݖଷଶ ' -ݖଵ ݖଶ ' ݖଵ ݖଷ ' ݖଶ ݖଷ . * ݖଵଶ ' ݖଶଶ ' ݖଷଶ ' ݖଵ ݖଶ ݖଷ ൬ ' ' ൰ ݖଷ ݖଶ ݖଵ * ݖଵଶ ' ݖଶଶ ' ݖଷଶ ' ݖଵ ݖଶ ݖଷ -ݖଵ ' ݖଶ ' ݖଷ . * ݖଵଶ ' ݖଶଶ ' ݖଷଶ ' ݖଵ ݖଶ ݖଷ ൫ݖଵ 'ݖଶ ' ݖଷ ൯ * ݖଵଶ ' ݖଶଶ ' ݖଷଶ ' ݖଵ ݖଶ ݖଷ -. * ݖଵଶ ' ݖଶଶ ' ݖଷଶ * *ݕଶ ܽܿ ' ݔܾ ' ݔ )/#&*%*)*! * ݔ$ * ݔെ * ଶ - െ !.-ݔ .- ' . ݇-ݔ ܽܿ ' ݔܾ ' ݔ ଵ $1-$ * ݕ * ݔെ ଼ *െ $ ݇- െ !.- ' . െ"݇ * െ$ ଵ * ݇ ଶ ଵ ଵ Hభ మ భ -௫ିହ.-௫ାଷ. మ -௫ ିଶ௫ିଵହ. మ ܽ * ܾ * െ ! ܿ * െ ξ ' ݔ݀ݔ݊݅ݏ A4 * * B4 >#(!3**#&*)*%.&()) ݔଶ െ ݕଶ * ܽ݊݀! * ݕݔ >#(!3,)*$)-($* %(#(-ܽ ' ܾ݅.+)$*( $ 4 $/)*+$*)+)*#%( "%(%+)#*%*%)%",*) &(%"# %+$*%"($)( #*%) >#(!3)+)**+*) െ ݅$*% *'+*%$$)&(*) ("$#$(/&(*) >#(!3%",)%($ %#)*+$*)+"*/$ )&(*$("$#$(/ &(*) ?#(!)3%((*$)-((%# %((*-%(!$ >#(!3#$%(((%($ "+"*%$) *+$*)-%+))+#)$ &(%+*%(%%*)#*%-( #%()+))+"4 %$*)($%*("4 $*%$ +*$6* (%%* ξଵା௦௫ξଵି௦௫ ݀ݔ ξଵି௦௫ ௦௫ ξଵି௦௫ ݀ݔ * െξ െ ݔ݊݅ݏG 30 distinct toys need to be equally divided into 10 packets. 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KILLARA HIGH SCHOOL LAST UPDATED AUGUST 23, 2017 18 (e) 2017 Mathematics Extension 2 HSC Trial Examination Solutions 2 marks Changing the limits and finding dx in terms of t 1 mark 1 mark 1 dt Correct substitution leading to 0 t22 +9 Correctly evaluating their integral 2π 0 dx dx 5 + 4 cos x t = tan x2 =⇒ cos x = ∴ 2π 0 1 − t2 1 + t2 ∴ x = tan−1 (2t) 2 dt ∴ dx = 1 + t2 x = 0 =⇒ t = 0 π x= =⇒ t = 1 2 2 dt 1 dx 1 + t2 dx = 1 − t2 5 + 4 cos x 0 5+4 1 + t2 2 dt 1 1 + t2 = 2 2 0 5(1 + t ) + 4(1 − t ) 1 + t2 2 dt = 01 2 t +9 1 t 1 −1 tan =2 3 3 0 2 1 = tan−1 3 3 Markers Comment: Very well done. LAST UPDATED AUGUST 23, 2017 KILLARA HIGH SCHOOL 20 2017 Mathematics Extension 2 HSC Trial Examination Solutions Question 13 (15 Marks) (a) i. 3 marks Correct proof with all correct reasons using correct terminology 2 marks Correct proof with 2 correct reasons 1 mark Significant progress towards proof with correct reasons ∠OAF = ∠ACO ∠OAF = ∠ACO = ∠COB In AF Oand EF O ∠AF O = ∠EF O ∠OAF = ∠EOF ∴ ∠AOF = ∠OEF ∴ F AO ||| F OE (the angle between a tangent and a chord through the point of contact is equal to the angle in the alternate segment) (alternate angles AC OB) (common) (proven above) (angle sum of a triangle) (equiangluar) Markers Comment: Generally quite well done but many still not being precise enough with proof - don’t take the risk of losing marks ii. 1 mark Correct ratios with correct reasoning FO FA = (corresponding sides in congruent triangles) FE OF ∴ OF 2 = EF × AF Markers Comment: Well done - but reason often not given LAST UPDATED AUGUST 23, 2017 KILLARA HIGH SCHOOL 2017 Mathematics Extension 2 HSC Trial Examination 21 iii. 2 marks Correct solution with correct reasoning 1 mark Significant progress but incorrect reasoning But AF × F E = F B 2 (The square of the length of the tangent fro external point is equal to the product o intercepts of the secant passing through this po ∴ OF 2 = F B 2 ∴ OF = F B ∴AE extended bisects OB Markers Comment: Very poorly done - this is the forgotten circle geometry theorem - Learn it! (b) For each of the graphs 1 mark Correct accurate shape with relevant intercepts and asymptotes labeled i. ii. KILLARA HIGH SCHOOL LAST UPDATED AUGUST 23, 2017 22 2017 Mathematics Extension 2 HSC Trial Examination Solutions iii. Markers Comment:Most were fairly well done although some students still not accurate enough with their graphs (c) 1 mark 1 mark Uses the double root property to establish a solution Logical reasoning leading to the desired result x3 + 3x + n = 0 If has a double root then : 3x2 + 3m = 0 √ 3 √ ∴ −m + 3m −m + n = 0 √ √ ∴ − −m + 3m −m = −n √ ∴ 2m −m = −n ∴ −4m3 = n2 √ =⇒ x = ± −m Markers Comment:Generally well done - no need to use complex numbers! LAST UPDATED AUGUST 23, 2017 KILLARA HIGH SCHOOL 2017 Mathematics Extension 2 HSC Trial Examination (d) 23 1 mark Finds correct radius and height 1 mark 1 mark 1 mark Establishing the integral V = 2π 0 (1 + x)(x − x2 ) dx Correct primitive function for their integral Correct solution for their integral 1 ΔV ∼ = 2πrhδx Radius of a typical shell = x + 1 Height of a typical shell = x − x2 1 ∴ V = 2π (1 + x)(x − x2 ) dx 0 1 = 2π (x − x3 ) dx 0 1 x2 x4 − = 2π 2 4 0 1 1 = 2π − 2 3 π = units3 2 Markers Comment:Generally very well done - those that made mistakes did so because they skipped steps KILLARA HIGH SCHOOL LAST UPDATED AUGUST 23, 2017 2017 Mathematics Extension 2 HSC Trial Examination 25 Question 15 (15 Marks) (a) i. 1 mark Splitting into parts correctly 1 mark Substituting into parts formula correctly 1 mark Resolving the parts formula to get desired reduction formula In = xn e2x dx u = xn ∴ In = (xn ) xn e2x 2 n 2x x e = 2 = n−1 1 2x e − nx 2 n − xn−1 e2x dx 2 n − In−1 2 u = nxn−1 1 2x e 2 1 v = e2x 2 v = e2x dx Markers Comment:Generally well done - some were not explicit enough with their parts integration and made errors. ii. 1 mark 1 mark Getting to 12 x2 e2x − 1 xe2x 2 − 12 I0 or similar place Correctly using reduction formula to obtain final result I2 = x2 e2x dx 1 = x2 e2x − I1 2 1 2 2x 1 2x 1 = x e − xe − I0 2 2 2 1 2 2x 1 2x 1 = x e − xe + x0 e2x dx 2 2 2 1 1 1 = x2 e2x − xe2x + e2x + C 2 2 4 e2x 2 2x − 2x + 1 + C = 4 Markers Comment:Skipping steps lead to sign errors - show all working KILLARA HIGH SCHOOL LAST UPDATED AUGUST 23, 2017 26 (b) 2017 Mathematics Extension 2 HSC Trial Examination i. 1 mark Solutions Correct result with working x3 + 5x2 − 2x − 3 = 0 ∴ α2 = (α + β + γ)2 − 2(α + β + γ) = 25 − 2(−2) = 29 Markers Comment:Well done 3 Generates the expression α + 15 α2 − 8 α − 9 = 0 or similar equivalent progress towards solutions ii. 1 mark 1mark substitutes in correctly to obtain desired result Substitute the roots into the polynomial ∴α3 + 5α2 − 2α − 3 = 0 β 3 + 5β 2 − 2β − 3 = 0 γ 3 + 5γ 2 − 2γ − 3 = 0 α2 − 2 α−9=0 ∴ α3 + 5 ∴ α3 = 9 − 5 α2 + 2 α = 9 − 5(29) + 2(−5) = −146 Markers Comment:Some students made very careless errors trying to skip steps - some were very inefficent iii. 1 mark Attempts to substitute in roots and manipulate or equivalent 1 1 1 significant progress producing the expression x − α x − β x − γ = 0 1mark Obtains desired solution 1 1 1 , and then α β γ 1 1 1 x− x− x− α β γ 1 1 1 ∴ −α −β −γ x x x 5 2 1 ∴ Equation is: 3 + 2 − − 3 = 0 x x x ∴1 + 5x − 2x2 − 3x3 = 0 ∴ 3x3 + 2x2 − 5x − 1 = 0 If the equation has roots =0 =0 Markers Comment:Generally well done - but solution must be a polynomial in x LAST UPDATED AUGUST 23, 2017 KILLARA HIGH SCHOOL 2017 Mathematics Extension 2 HSC Trial Examination (c) 27 ı 2 marks i. Correctly deriving expression for g with appropriate reasoning. 1 mark Corresponding expression for h and f The base of the solid is a trapezium and it’s area is the sum of the two trapezia. x (e − x) e (a + g) ∴ (a + c) = (g + c) + 2 2 2 ∴ e(a + c) = x(g + c) + (e − x)(a + g) + ce = + cx + ∴ ae gx ae −gx ∴ ge = ce + ax − cx =⇒ g = c + a−c x e Similarly (using the same reason as part i.) h=d+ b−d e x and a x e Markers Comment:Not very well done - many tried to use linear expressions without defining where any axes are - lots of fudging to get desired result. Most only got 1 mark f= KILLARA HIGH SCHOOL LAST UPDATED AUGUST 23, 2017 28 2017 Mathematics Extension 2 HSC Trial Examination ii. 1 mark 1 mark Solutions Correct expression for V (x) Significant progress towards the final solution x d + (b−d) (2a − c) e x Now A(x) = c + e 2 e cd bc + 2ad − 2cd 2a − c b−d 2 ∴ V (x) = .dx + x+ x 2 2e 2e e 0 e bc + 2ad − 2cd x2 2a − c b − d x3 cd x+ + = 2 2e 2 2e e 3 0 2 3 b−d e cd bc + 2ad − 2cd e 2a − c = e+ + 2 2e 2 2e e 3 e {6cd + 3bc + 6ad − 4cd + 4ab − 4ad − 2bc + 2cd} = 12 e = {2cd + bc + 2ad + 4ab} 12 b+d 2 Alternatively solve by Simpson’s rule using A1 = 12 cd, A2 = a2 + a+c 2 2 and A3 = ab which gives: b+d e 1 a a+c 2 V = cd + 4 + + 2ab 6 2 2 2 2 yielding the same result. Markers Comment:Quite poorly done - it seems as if many were intimidated by a simple integral - no one fully simplified and no one thought to use Simpson’s rule since it is quadratic - much easier! LAST UPDATED AUGUST 23, 2017 KILLARA HIGH SCHOOL