Amrita School of Engineering
B.Tech. II Semester
23MAT130 - Engineering Mathematics II
Tutorial 5
(Inner product space, orthogonality)
1. Let 𝑢 = (𝑢1 , 𝑢2 , 𝑢3 ), 𝑣 = (𝑣1 , 𝑣2 , 𝑣3 ). Determine whether the given function 〈𝑢, 𝑣〉 = 𝑢1 𝑣1 + 𝑢3 𝑣3
is an inner product on 𝑅 3 . If not, list the axioms that do not hold.
2. Suppose that 𝑢, 𝑣 and 𝑤 are vectors such that
〈𝑢, 𝑣〉 = 2, 〈𝑣, 𝑤〉 = −3 , 〈𝑢, 𝑣〉 = −3, 〈𝑢, 𝑤〉 = 5, ‖𝑢‖ = 1, ‖𝑣‖ = 2, ‖𝑤‖ = 7 .
Evaluate the given expression
a) 〈𝑢 − 𝑣 − 2𝑤, 4𝑢 + 𝑣〉
b) ‖𝑢 − 2𝑣 + 4𝑤‖
3. Sketch the unit circle in 𝑅 2 using the given inner product
1 1
a) 〈𝑢, 𝑣〉 = 9 𝑢1 𝑣1 + 25 𝑢2 𝑣2
1 1
b) 〈𝑢, 𝑣〉 = 25 𝑢1 𝑣1 + 16 𝑢2 𝑣2
𝑐) 〈𝑢, 𝑣〉 = 2𝑢1 𝑣1 + 𝑢2 𝑣2
4. Let 𝑅 3 have the Euclidean inner product. Let 𝑢 = (1, 1, −1), 𝑣 = (6,7, −15).
a) If ‖𝑘𝑢 + 𝑣‖ = 13, what is 𝑘?
b) Find 𝑑(𝑢, 𝑣)
5. Find the cosine of the angle between 𝑢 𝑎𝑛𝑑 𝑣 with respect to appropriate inner product spaces.
a) 𝑢 = (1, 0, 1, 0), 𝑣 = (−3, −3, −3, −3) in 𝑅 4
b) 𝑝 = 1 − 𝑥 + 2𝑥 2 , 𝑞 = 2𝑥 + 𝑥 2 in 𝑃2
9 8 7 1 2 3
c) 𝐴 = [ ] and 𝐵 = [ ] in 𝑀2𝑥2 where 〈𝐴, 𝐵〉 = 𝑡𝑟(𝐵 𝑇 𝐴)
6 5 4 4 5 6
6. Find a non-zero vector 𝑤 that is orthogonal to 𝑢1 = (1, 2, 1) and 𝑢2 = (2, 5, 4) in 𝑅 3 .
7. For what values of 𝑘 the vectors are orthogonal?
a) 𝑢 = (𝑘, 𝑘, 1), 𝑣 = (𝑘, 5, 6) in 𝑅 3
2 1 1 1
b) 𝐴 = [ ], 𝐵 = [ ] in 𝑀2𝑥2 where 〈𝐴, 𝐵〉 = 𝑡𝑟(𝐵 𝑇 𝐴)
−1 3 𝑘 −1
8. Verify the Cauchy-Schwarz inequality using the Euclidean inner product for the vectors 𝑢 = (3, 2),
𝑣 = (4, −1) where Cauchy-Schwarz inequality is |〈𝑢, 𝑣〉| ≤ ‖𝑢‖ ‖𝑣‖.
0 4/5 −3/5
9. Check whether S={(0) , (3/5) , ( 4/5 )} forms an orthonormal basis for R3. If yes, express (1, -1, 2),
1 0 0
(3, 5, 7) and (2, 0, 8) as linear combinations of the elements in S.
10. State True or False:
a. If all row vectors of a matrix form an orthonormal system, then the column vectors of the matrix also
will form an orthonormal system.
b. If S is a set of orthonormal vectors, then S will also be a linearly independent set.