Question

r vector equal to a vector +b vector prove that r square is equal to a square + b square + 2abcos​

Answer 1

rv = av+bv

=>rv.rv = (av+bv).(av+bv)

=>|r|.|r|.cos0° = av.av+av.bv+bv.av+bv.bv

=>r² = |a|.|a|.cos0°+|b|.|b|.cos0°+2av.bv

=>r² = a²+b²+2|a||b|cosθ = a²+b²+2abcosθ

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Answer 2

Step-by-step explanation:

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