Course 5 Wk 2 A1 : Optional quick questions

Hi all,

I’ve got solutions for the two optional exercises, but am off by a factor of ~15% for both calculations

Is there an error in the following translation from calculation to code?

“”"
Ex3: Neutralize
redacted
“”"
I’m getting -3.8510^-17 instead of ~4.410^-17

“”"
Ex4:

redacted
“”"
I’m getting +~0.6 instead of ±0.77

For neutralize(), both your answers are essentially zero (there is a note in the instructions about this). The difference is likely because using norm() internally computes the square root, and then you have to square it again - that loses numerical precision.

Same explanation in Ex. 4 - squaring the norm is less accurate than computing the sum of the squares and not computing the square root.

Also please don’t post your code on the Forums.

Thanks tmosh

That’s right re: effectively zero answers. I figure that the percent-wise difference is due to a coding math error of sorts. For both exercises, I was previously using the square root of the sum of square,
(i.e.

sqrt(sum( x^2))
and
(sqrt(sum(x^2))^2)

) and receiving the same numerical result as I am currently.

Does that notation seem correct, or is there another function that isn’t np.linalg.norm? I noticed you explicitly stated not to compute the square root.

Code has been redacted, I just put it up briefly so a mentor could see it.

friendly bump if you know how to solve the problem

So, based on the justification provided, is it okay to assume the values -3.85 10^-17 (for Ex.3) and +~0.6 (for Ex.4) are acceptable ?
I just wanted to make sure as I have also got the same results and I have verified that I am using the right formulas as mentioned in the assignment.