Question

What is known about Θ, the angle between two nonzero vectors u and v, if each of the following is true? Explain your answers.

Answer 1

The angle between two nonzero vectors u and v is given by

Cos Θ=u*v/║u║║v║

1) If u*v=0, then CosΘ=0

arccos 0=90°

2) If u*v > 0, then CosΘ >0

If (cos Θ > 0, then Θ is less than 90°

3) If u*v < 0, then Cos Θ < 0

If Cos Θ < 0, then Θ is greater than 90°

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