Finding angle given a 3d vectors

[nicholaskong100]

Find the angle ? between the vectors.

I find the dot product and norm. But I cannot figure out why my angle is incorrect. Answer is written in purple.

 

[Deleted member 4993]

Find the angle ? between the vectors.

I find the dot product and norm. But I cannot figure out why my angle is incorrect. Answer is written in purple.

View attachment 33548

Why do you think that your answer is incorrect?