hi can you please explain questions of quiz Angles between vectors using a non-standard inner product Graded Quiz • 20 min

[manish-rocks]

hi can you please explain questions of quiz Angles between vectors using a non-standard inner product Graded Quiz • 20 min
Because i am not able to get the answer . I tried by myself but getting different answers .

[samuelimoisili]

Is it in the linear algebra course?

[samuelimoisili]

Let me know I would be glad to help out.

[ewelinaewela]

For example, from Q1:

x = [1,1]
y= [-1,1]
A = ([(2,-1), (-1, 4)])

cos(angle) = x.T@A@y / sqrt(x.T@A@x * y.T@A@y) = 2 / sqrt (4 * 8) = 0.35

to get the angle you do not look for cos of 0.35, but the inverse of cos(0.35)

in python
you use np.arccos, as explained here: https://numpy.org/doc/stable/reference/generated/numpy.arccos.html

detailed math explanation:
https://mathonweb.com/help_ebook/html/functions_2.htm

I think this is the main confusion in this quiz. All questions are with the same trick.

[GLOMQuyet]

thank you