Let and be three vectors. Find the values of x for which the angle between and is acute and the angle between and is obtuse

We know that,


Where, x is the angle between two vectors


Applying for





Since angle between is acute cos x should be greater than 0



x2 – 4 > 0


x > 2 and x < –2


applying for




Since angle between is obtuse cos x should be less than


0



x2 – 9 < 0


x > –3 and x < 3


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