Question

If a=i-2j and b=i+k then the value of cos theta is

Answer 1

Answer:

What is the angle between 2 vectors A=i-j and B=j+k?

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A⃗ =i−j|A⃗ |=1+1−−−−√=2–√

B⃗ =j+k|B⃗ |=1+1−−−−√=2–√

Letθbe the angle between two vectors

A⃗ ⋅B⃗ =|A⃗ ||B⃗ |cosθ

⟹1(0)+(−1)(1)+0(1)=2cosθ

⟹cosθ=−12

⟹θ=cos−1−12=120∘or240∘