Details scalcets,
a) If u is unit vector , then, ⃗u.⃗v = 1/2 and ⃗u.⃗w = - 1/2 where v and w also unit vectors.
b) Exact value of angle between the vectors is 34.3803442 and Approximation value, 34.4..
c) Exact value of the angle between the vectors, a = 71 - 2j + k, b = 3i - k is 30.60889766 ~ 30.61 (approximation value).
In mathematics, a unit vector is defined as a normed vector space is a vector of length one.
a) If u is a unit vector , we have to calculate ⃗u.⃗v and ⃗u.⃗w where v and w are also unit vectors.
We know that, Angle between two vectors θ is
Cosθ = u⃗ .⃗v/|u| |v|
=> cos 60° |u| |v| = ⃗u.⃗v
=> ⃗u.⃗v = 1/2(1)(1) = 1/2
Also, Cosθ = ⃗u.⃗v/|u| |w|
=> Cosθ |u| |w| = ⃗u.⃗w
=> ⃗u.⃗w = cos 120° (1)(1)
=> ⃗u.⃗w = -1/2
So, ⃗u.⃗v = 1/2 and ⃗u.⃗w = - 1/2
b) We have, a = (7,2), b = (3,-1)
Cosθ = a.b/|a| |b|
|a| = √(7)²+ (2)² = √49+4 = √53
|b| = √(3)²+ (-1)²= √9+1 = √10
a.b = 7×3 - 2×1 = 21 - 2 = 19
so, Cos θ = 19/√10 (√53) = 19/√530
=> θ = Cos⁻¹( 19/√530)
=> θ = 34.3803442 ~ 34.4
c) We have, a = 7i - 2j + k, b = 3i - k
Cos θ = a.b/|a| |b|
|a| = √(7)² + (-2)² +(1)² = √49+4+1 = √54
|b| = √(3)²+ 0 +(-1)² = √9+1 = √10
a.b = (7i - 2j + k).(3i - k) = 21 -0 - 1 = 20
Cosθ = 20/√10√54 = 20/√540
θ = cos⁻¹(20/√540) = 30.60889766 ~ 30.61
To learn more about unit vector , refer:
https://brainly.com/question/29404877
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