Question

heya users !!!!!!

solve the 3rd question ....

Answer 1

Here is your answer

Here, a + 2b and 5a - 4b are perpendicular to each other, so

(a + 2b).(5a - 4b) = 0

(5|a|2 - 4a.b + 10a.b - 8|b|2) = 0

(5 + 6a.b - 8) = 0

a.b = 1/2
|a||b| cos θ =1/2

(Since a and b are unit vectors)

cos θ = cos 60
θ = 60
Hence the required angle is 60°

I hope it's help you

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