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[MAA 3.17-3.19] PLANES

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INTERNATIONAL BACCALAUREATE
Mathematics: analysis and approaches
MAA
EXERCISES [MAA 3.17-3.19]
PLANES
Compiled by Christos Nikolaidis
O.
1.
Practice questions
[Maximum mark: 10]
[without GDC]
1
 2


 
Consider the point A(2, 1, 5) and the vectors b   0  and c   1  .
 3
 4
 
 
(a)
Write down the vector equation of the plane Π that passes through the point A
and is parallel to the vectors b and c .
[2]
(b)
Find the vector b  c .
[3]
(c)
The equation of the plane Π can be written in the form r  n  a  n . Write down
(d)
the vectors n and a .
[2]
Hence, find the Cartesian equation ax  by  cz  d of the plane Π .
[3]
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Page 1
[MAA 3.17-3.19] PLANES
2.
[Maximum mark: 10]
[without GDC]
Consider the points A(2, 1,  5) , B(1, 1, 1) and C(3,  1,  2) .
(a)
Find the vectors AB  AC .
[4]
Hence,
(b)
find the Cartesian equation of the plane of the triangle ABC.
[3]
(c)
find the area of the parallelogram defined by the vectors AB, AC .
[2]
(d)
find the area of the triangle ABC.
[1]
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Page 2
[MAA 3.17-3.19] PLANES
3.
[Maximum mark: 12]
[with GDC]
The point A (2, 5, –1) is on the line L , which is perpendicular to the plane with equation
x  y  z 1  0
(a)
Find the Cartesian equation of the line L .
[2]
(b)
Find the point of intersection of the line L and the plane.
[4]
(c)
The point A is reflected in the plane. Find the coordinates of the image of A.
[2]
(d)
Calculate the distance from the point B(2, 0, 6) to the line L .
[4]
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Page 3
[MAA 3.17-3.19] PLANES
4.
[Maximum mark: 21]
[with GDC]
Consider the lines
1
 2
 
 
L1 : r   2     3 
 3
1
 
 
 1
 4
 
 
L2 : r  1    7 
 1
 4
 
 
and the planes
Π1 :
2x  3y  z  7
Π2 :
4 x  7 y  4 z  19
Find the following.
(a)
The acute angle between the lines L1 and L2 .
[4]
(b)
The acute angle between the planes Π1 and Π2 .
[1]
(c)
The acute angle between the line L1 and the plane Π 2 .
[2]
(d)
The acute angle between the y -axis and the plane Π 2 .
[3]
(e)
The point of intersection of the lines L1 and L2 .
[5]
(f)
The point of intersection of the line L1 and plane Π1 .
[3]
(g)
The line of intersection of the planes Π1 and Π2 .
[3]
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Page 4
[MAA 3.17-3.19] PLANES
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Page 5
[MAA 3.17-3.19] PLANES
A.
5.
Exam style questions (SHORT)
[Maximum mark: 6]
(a)
(b)
[without GDC]
If u = i +2j + 3k and v = 2i – j + 2k, show that
u × v = 7 i + 4 j – 5 k.
[2]
Let w = λu + μv where  and  are scalars. Show that w is perpendicular to the
line of intersection of the planes x  2 y  3 z  5 and 2 x  y  2 z  7 for all values
of  and  .
[4]
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6.
[Maximum mark: 6]
[with GDC]
 4 
 
A ray of light coming from the point (−1, 3, 2) is travelling in the direction of vector  1 
  2
 
and meets the plane  : x  3 y  2 z  24  0 . Find the angle that the ray of light makes
with the plane.
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Page 6
[MAA 3.17-3.19] PLANES
7.
[Maximum mark: 6]
The line
[with GDC]
x 1 y  2 z  1
is reflected in the plane x  y  z  1 . Calculate the angle


1
2
2
between the line and its reflection. Give your answer in radians.
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8.
[Maximum mark: 6]
[with GDC]
Find the cosine of the angle  between the planes  1 and  2 , where
 1 has equation 2 x  y  z  2 and  2 has equation x  2 y  z  6 .
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9.
[Maximum mark: 6]
[with GDC]
Find the angle between the plane 3 x  2 y  4 z  12 and the z -axis. Give your answer
to the nearest degree.
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Page 7
[MAA 3.17-3.19] PLANES
10.
[Maximum mark: 6]
[without GDC]
Consider the point A(1, −1, 4) and the line L2 with equation r = 2i+4j +7k + t(2i +j +3k)
where t  . Find the Cartesian equation of the plane that contains both the line L2 and
point A.
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11.
[Maximum mark: 6]
[without GDC]
Find an equation of the plane containing the two lines
x –1
1– y
x 1 2 – y z  2
.
 z – 2 and


2
3
3
5
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Page 8
[MAA 3.17-3.19] PLANES
12.
[Maximum mark: 6]
[without GDC]
 2
 
x4 y2 z 6
A plane Π has equation r    1  16 and a line l has equations


2
4
1
1
 
Show that the line l lies in the plane.
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13.
[Maximum mark: 5]
[without GDC]
The plane 6 x  2 y  z  11 contains the line x  1 
y 1 z  3
. Find l .

2
l
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Page 9
[MAA 3.17-3.19] PLANES
14.
[Maximum mark: 5]
[without GDC]
Find the coordinates of the point where the line given by the parametric equations
x  2  4 , y    2 , z  3  2 , intersects the plane with equation 2 x  3 y  z  2 .
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15.
[Maximum mark: 5]
[without GDC]
Find the coordinates of the point of intersection of the line L with the plane P where:
x  3 y –1 z –1


2
–1
2
P :2x  3y – z  – 5
L:
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Page 10
[MAA 3.17-3.19] PLANES
16.
[Maximum mark: 6]
[without GDC]
The line r = i + k + μ(i – j + 2k) and the plane 2 x  y  z  2  0 intersect at the point P.
Find the coordinates of P.
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17.
[Maximum mark: 6]
The line
[without GDC]
x3
5 z
and the plane 2 x  y  3 z  10 intersect at the point P.
 y 1 
2
3
Find the coordinates of P.
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Page 11
[MAA 3.17-3.19] PLANES
18.
[Maximum mark: 5]
[with / without GDC]
Find the equation of the line of intersection of the two planes
4 x  y  z  2 and 3 x  y  2 z  1 .
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19.
[Maximum mark: 5
[with / without GDC]
Find an equation for the line of intersection of the following two planes.
x  2 y  3z  2
2x  3 y  5z  3
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Page 12
[MAA 3.17-3.19] PLANES
20.
[Maximum mark: 6]
[without GDC]
The point A is the foot of the perpendicular from the point (1, 1, 9) to the plane
2 x  y  z  6 . Find the coordinates of A.
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21.
[Maximum mark: 6]
[without GDC]
Let P be the point (1, 0, – 2) and Π be the plane x  y  2 z  3  0 . Let P΄ be the
reflection of P in the plane Π . Find the coordinates of the point P΄.
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Page 13
[MAA 3.17-3.19] PLANES
22.
[Maximum mark: 8]
[without GDC]
Three points A, B and C have coordinates (2, 1,–2), (2,–1,–1) and (1, 2, 2) respectively.
The vectors OA , OB and OC , where O is the origin, form three concurrent edges of a
parallelepiped OAPBCQSR as shown in the following diagram.
P
S
A
Q
B
R
O
C
(a)
Find the coordinates of P, Q, R and S.
[4]
(b)
Find an equation for the plane OAPB.
[2]
(c)
Calculate the volume, V, of the parallelepiped given that V = OA  OB  OC .
[2]
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Page 14
[MAA 3.17-3.19] PLANES
INTERSECTION OF THREE PLANES
23.
[Maximum mark: 22]
[without GDC]
Please revisit the exercises on paragraph [MAA 1.10] SYSTEMS OF LINEAR EQUATIONS
Complete the table below.
Geometric relationship of the three planes
(state the vector equation of the line of intersection if applicable)
[MAA 1.10]
Exercise
(i) The intersection point of the three planes is (1, 1,1)
(ii) There is no point of intersection. The three planes form a prism
1
2
3
4
5
6
If k  3 :
7
If k  3 :
If k  5 :
8
If k  5 :
1
3
If k  3, :
9
If k 
1
:
3
If k  3 :
If a  1 :
10
If a  1 :
If k  1 :
11
0
1
0
 
1
 
(iii) The three planes intersect in the straight line: r   3     2 
 
 
If k  1 :
Page 15
[MAA 3.17-3.19] PLANES
B.
24.
Exam style questions (LONG)
[Maximum mark: 12]
(a)
[with GDC]
The point P(1, 2, 11) lies in the plane  1 . The vector 3i – 4 j + k is perpendicular
to  1 . Find the Cartesian equation of  1 .
(b)
(c)
[2]
The plane  2 has equation x  3 y  z  4 .
(i)
Show that the point P also lies in the plane  2 .
(ii)
Find a vector equation of the line of intersection of  1 and  2 .
Find the acute angle between  1 and  2 .
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Page 16
[5]
[5]
[MAA 3.17-3.19] PLANES
25.
[Maximum mark: 11]
[without GDC]
The plane  contains the line
x 1 y 1 z  5
and the point (1, 2,3) .


2
3
6
(a)
Show that the equation of  is 6 x  2 y  3 z  7 .
[7]
(b)
Calculate the distance of the plane  from the origin.
[4]
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Page 17
[MAA 3.17-3.19] PLANES
26.
[Maximum mark: 13]
[with GDC]
A plane π1 has equation
(a)
6
 
r   5   15 .
 4
 
A point P ( p,  p, p ) lies on plane π1 and Q is the point where the plane π1 meets
the y -axis.
(i) Find the coordinates of P and of Q.
(ii) Show that PQ is parallel to the vector u, where u = i – 2j + k.
(b)
[5]
Another plane π2 intersects π1 in the line (PQ). The point T(1,0,–1) lies on π2 .
(i) Find the equation of π2 , giving your answer in the form Ax+By+Cz = D.
(ii) Find the angle between π1 and π2 .
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Page 18
[8]
[MAA 3.17-3.19] PLANES
27.
[Maximum mark: 13]
(a)
[with / without GDC]
Solve the following system of linear equations
x  3 y  2 z  6
2 x  y  3z  7
3x  y  z  6
[3]
(b)
Find the vector v = (i + 3j – 2k) × (2i + j + 3k).
(c)
If a = i + 3j – 2k, b = 2i + j + 3k and u = ma + nb where m, n are scalars, and
u  0 , show that v is perpendicular to u for all m and n.
(d)
[3]
[3]
The line l lies in the plane 3 x  y  z  6 , passes through the point (1, –1, 2)
and is perpendicular to v. Find the equation of l .
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Page 19
[4]
[MAA 3.17-3.19] PLANES
28.
[Maximum mark: 22]
[with GDC]
The coordinates of the points P, Q, R and S are (4,1,–1), (3,3,5), (1,0, 2c), and (1,1,2),
respectively.
(a)
Find the value of c so that the vectors QR and PR are orthogonal.
[7]
For the remainder of the question, use the value of c found in part (a) for the
coordinate of the point R .
(b)
Evaluate PS × PR .
[4]
(c)
Find an equation of the line l which passes through the point Q and is parallel to
the vector PR .
(d)
(e)
[3]
Find an equation of the plane  which contains the line l and passes through the
point S.
[4]
Find the shortest distance between the point P and the plane  .
[4]
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Page 20
[MAA 3.17-3.19] PLANES
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Page 21
[MAA 3.17-3.19] PLANES
29.
[Maximum mark: 25]
[without GDC]
Consider the points A(1, 2, 1), B(0, –1, 2), C(1, 0, 2) and D(2, –1, –6).
(a)
Find the vectors AB and BC .
[2]
(b)
Calculate AB BC .
[2]
(c)
Hence, or otherwise find the area of triangle ABC .
[3]
(d)
Find the Cartesian equation of the plane P containing the points A , B and C .
[3]
(e)
Find a set of parametric equations for the line L through the point D and
perpendicular to the plane P .
[3]
(f)
Find the point of intersection E , of the line L and the plane P .
[4]
(g)
Find the distance from the point D to the plane P .
[2]
(h)
Find a unit vector that is perpendicular to the plane P .
[2]
(i)
The point F is a reflection of D in the plane P . Find the coordinates of F.
[4]
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Page 22
[MAA 3.17-3.19] PLANES
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Page 23
[MAA 3.17-3.19] PLANES
30.
[Maximum mark: 16]
[without GDC]
The points A, B, C, D have the following coordinates
A : (1, 3, 1) B : (1, 2, 4) C : (2, 3, 6) D : (5, – 2, 1).
(a)
(i)
Evaluate the vector product AB × AC , giving your answer in terms of the
unit vectors i, j, k.
(ii)
Find the area of the triangle ABC.
[6]
The plane containing the points A, B, C is denoted by Π and the line passing through
D perpendicular to Π is denoted by L. The point of intersection of L and Π is denoted
by P.
(b)
(i)
Find the cartesian equation of Π .
(ii)
Find the cartesian equations of L.
[5]
(c)
Determine the coordinates of P.
[3]
(d)
Find the perpendicular distance of D from Π .
[2]
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Page 24
[MAA 3.17-3.19] PLANES
31.
[Maximum mark: 16]
A line l1 has equation
[without GDC]
x  2 y z 9
 
. Let M be a point on l1 with parameter μ.
2
3
1
(a)
Express the coordinates of M in terms of μ.
(b)
The line l2 is parallel to l1 and passes through P(4, 0, –3).
(i)
(c)
(ii)
Express PM in terms of μ.
Find the value of μ.
(ii) Find the distance between l1 and l2.
[5]
The plane  1 contains l1 and l2. Find an equation for  1 , giving your answer in the
form Ax + By + Cz = D.
(e)
[4]
The vector PM is perpendicular to l1.
(i)
(d)
Write down an equation for l2.
[1]
[4]
The plane  2 has equation x  5 y  z  11 . Verify that l1 is the line of
intersection of the planes  1 and  2 .
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Page 25
[2]
[MAA 3.17-3.19] PLANES
32.
[Maximum mark: 29]
(a)
Show that lines
[without GDC]
x2 y 2 z 3
x2 y 3 z 4


and


intersect and find
1
3
1
1
4
2
the coordinates of P, the point of intersection.
[8]
(b)
Find the Cartesian equation of the plane Π that contains the two lines.
[6]
(c)
The point Q (3, 4, 3) lies on Π . The line L passes through the midpoint of [PQ].
Point S is on L such that PS  QS  3 , and the triangle PQS is normal to the plane
Π . Given that there are two possible positions for S, find their coordinates.
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Page 26
[15]
[MAA 3.17-3.19] PLANES
33.
[Maximum mark: 12]
(a)
[with / without GDC]
 2
  2
 1 
 
 
 
The plane  1 has equation r =  1     1      3  .
1
 8 
  9
 
 
 
 2   1   1
     
The plane  2 has the equation r =  0   s 2   t 1 .
 1   1   1
     
(b)
(c)
(i)
For points which lie in  1 and  2 , show that,    .
(ii)
Hence, find a vector equation of the line of intersection of  1 and  2 .
[5]
y
The plane  3 contains the line 2  x 
 z  1 and is perpendicular to
3
4
3i – 2j + k. Find the Cartesian equation of  3 .
[4]
Find the intersection of  1 ,  2 and  3 .
[3]
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Page 27
[MAA 3.17-3.19] PLANES
34.
[Maximum mark: 14]
(a)
[without GDC]
The line l1 passes through the point A(0, 1, 2) and is perpendicular to the plane
x  4 y  3 z  0 . Find the Cartesian equation of l1 .
(b)
The line l2 is parallel to l1 and passes through the point P(3,  8,  11) . Find the
vector equation of the line l2 .
(c)
[2]
(i)
[2]
The point Q is on the line l1 such that PQ is perpendicular to l1 and l2 .
Find the coordinates of Q .
(ii)
Hence find the distance between l1 and l2 .
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Page 28
[10]
[MAA 3.17-3.19] PLANES
35.
[Maximum mark: 21]
[with / without GDC]
Consider the points A(2, –1, 0), B(3, 0, 1) and C(1, m, 2), where m  ℤ, m  0 .
(a)
(i)
2
, show that m  1 .
3
Determine the Cartesian equation of the plane ABC .
Find the area of the triangle ABC .
(i) The line L is perpendicular to plane ABC and passes through A . Find a
vector equation of L .
(ii) The point D(6, –7, 2) lies on L . Find the volume of the pyramid ABCD .
(ii)
(b)
(c)
(d)
Find the scalar product BA  BC .
ˆ  arccos
Hence, given that ABC
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Page 29
[6]
[4]
[3]
[8]
[MAA 3.17-3.19] PLANES
36.
[Maximum mark: 23]
[without GDC]
Two planes  1 and  2 are represented be the equations
3
 2 
 2





 1 : r   1     2     1 
5
 3
0
 
 
 
 2 : 2x  y  2z  4
(a)
(i)
 2   2 
   
Find  2    1 
 3  0
   
(ii)
Show that the equation of  1 can be written as x  2 y  2 z  11 .
(b)
Show that  1 is perpendicular to  2 .
(c)
The line l1 is the line of intersection of  1 and  2 .
Find the vector equation of l1 , giving the answer in parametric form.
(d)
[4]
[5]
The line l2 is parallel to both  1 and  2 , and passes through P(3,  5,  1) .
Find an equation for l2 in Cartesian form.
(e)
[4]
[3]
Let Q be the foot of the perpendicular from P to the plane  2 .
(i)
Find the coordinates of Q .
(ii)
Find PQ .
[7]
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Page 30
[MAA 3.17-3.19] PLANES
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Page 31
[MAA 3.17-3.19] PLANES
37.
[Maximum mark: 27]
[with GDC]
Consider the vectors a = i – j + k, b = i + 2 j + 4k and c = 2i –5 j – k.
(a)
Given that c = ma + nb where m, n  ℤ , find the value of m and of n .
[5]
(b)
Find a unit vector, u, normal to both a and b.
[5]
(c)
The plane  1 contains the point (1,  1,1) and is normal to b. The plane
intersects the x , y and z axes at the points L , M and N respectively.
(d)
(e)
(i)
Find a Cartesian equation of  1 .
(ii)
Write down the coordinates of L , M and N .
[5]
The line through the origin, O , normal to  1 meets  1 at the point P .
(i)
Find the coordinates of P .
(ii)
Hence find the distance of  1 from the origin.
[7]
The plane  2 has equation x  2 y  4 z  4 . Calculate the angle between  2 and
a line parallel to a.
[5]
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Page 32
[MAA 3.17-3.19] PLANES
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Page 33
[MAA 3.17-3.19] PLANES
38.
[Maximum mark: 18]
(a)
[with / without GDC]
Write the vector equations of the following lines in parametric form.
 3
2
 
 
r1 =  2   m  1
7
2
 
 
1  4 
   
r2 =  4   n  1
 2  1 
   
[2]
(b)
Hence show that these two lines intersect and find the point of intersection, A.
[5]
(c)
Find the Cartesian equation of the plane Π that contains these two lines.
[4]
(d)
  8
 3
 
 
Let B be the point of intersection of the plane Π and the line r =   3     8  .
 0 
 2
 
 
Find the coordinates of B.
(e)
[4]
If C is the mid-point of AB, find the vector equation of the line perpendicular to the
plane Π and passing through C.
[3]
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Page 34
[MAA 3.17-3.19] PLANES
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Page 35
[MAA 3.17-3.19] PLANES
39.
[Maximum mark: 20]
[without GDC]
The points A, B, C have position vectors i + j + 2k, i + 2 j + 3k, 3i + k respectively and
lie in the plane  .
(a)
Find the area of the triangle ABC;
[6]
(b)
Hence, or otherwise, find the shortest distance from C to the line AB;
[4]
(c)
Find the Cartesian equation of the plane  .
[4]
The line L passes through the origin and is normal to the plane  , it intersects  at D.
(d)
Find the coordinates of the point D;
[5]
(e)
Find the distance of  from the origin.
[1]
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