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Unit 3 Question 1. How do you prove that three 3-D points, A, B and C, are collinear ?. Answer to Unit 3 Question 1. Prove that vector AB is a multiple of vector BC AB = k BC And state that B is common to both vectors. Unit 3 Question 2. How do you add or subtract vectors ?.
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Unit 3 Question 1 • How do you prove that three 3-D points, A, B and C, are collinear ? 3.1
Answer to Unit 3 Question 1 • Prove that vector AB is a multiple of vector BC AB = k BC • And state that B is common to both vectors
Unit 3 Question 2 • How do you add or subtract vectors ? 3.1
Answer to Unit 3 Question 2 • add or subtract matching components
Unit 3 Question 3 • State the three rules of logs? 3.3
Answer to Unit 3 Question 3 • (i) logaxy = logax + logay • (ii) loga = logax – logay • (iii) logaxn = nlogax x y
Unit 3 Question 4 • What does ksin(x-a) expand out to? 3.4
Answer to Unit 3 Question 4 • ksinxcosa-kcosxsina
Unit 3 Question 5 a b c • If u = then what is u? 3.1
Answer to Unit 3 Question 5 • work out length √(a2+b2+c2)
Unit 3 Question 6 • What does • a.aequal ? 3.1
Unit 3 Question 7 • Express the equation y=kxn in the form of the equation of a straight line, Y=nX+c. 3.3
Answer to Unit 3 Question 7 • logy = nlogx + logk
Unit 3 Question 8 • How do you show that two vectors are perpendicular ? 3.1
a b Answer to Unit 3 Question 8 • Show that a.b=0
Unit 3 Question 9 • What do you get when you differentiate cosx ? 3.2
Answer to Unit 3 Question 9 • -sinx
Unit 3 Question 10 • What is • logax – logay equal to ? 3.3
Answer to Unit 3 Question 10 • x loga y
Unit 3 Question 11 • How do you name the angle between a line and a plane ? 3.1
A C B Answer to Unit 3 Question 11 • (i) start at end of line (A) • (ii) go to where line meets the plane (B) • (iii) go to the point on the plane directly under the start of the line (C) • (iv) Answer is ABC
Unit 3 Question 12 • What is a position vector ? 3.1
Answer to Unit 3 Question 12 • A vector which startsat the origin
Unit 3 Question 13 • What do you get when you differentiatesin x? 3.2
Answer to Unit 3 Question 13 • cos x
Unit 3 Question 14 • How do you integrate cos ax ? 3.2
Answer to Unit 3 Question 14 • 1/a sin ax + C
Unit 3 Question 15 • What do you get when you differentiate • cosax ? 3.2
Answer to Unit 3 Question 15 • -asinax
Unit 3 Question 16 • How would you differentiate a function like y = sin ax? 3.2
Answer to Unit 3 Question 16 • dy/dx = acos ax
Unit 3 Question 17 • What is logaa equal to ? 3.3 and 1.2
Unit 3 Question 18 • What is loga1 equal to ? 3.3 and 1.2
Unit 3 Question 19 • How do you express acosx+bsinx+c in the form kcos(x- α)? 3.4
Answer to Unit 3 Question 19 • (i) expand brackets and equate like terms • (ii) find k =√(a2+b2) • (iii) identify quadrant α is in • (iv) find α using tanα = sinα cosα S A T C
Unit 3 Question 20 • How do you solve an equation of the form acosx + bsinx + c=0? 3.4
Answer to Unit 3 Question 20 • Change acosx+bsinx into Rcos(x- a) • rearrange and solve