Question

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Answer 1

Given,
a and b are two unit vector.
So,
|a|= 1

|b|=1

Since,
a+ 2b and 5a -4b perpendicular to each other then their dot product will be zero.

→(a + 2b).(5a - 4b) = 0

→(5|a|2 - 4a.b + 10a.b - 8|b|2) = 0

→(5 + 6a.b - 8) = 0
→6a.b =3

→a.b= 1/2

→ |a| |b| cosø = 1/2. (where ø angle between vector a and vector b)

→cosø =1/2

→cosø =cosπ/3

→ø =π/3.

Answer 2

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