Hi Everyone,
I have the same issue
What you see in the printed lines is:
print(theta_plus, theta_minus, J_plus, J_minus, gradapprox)
print(grad)
print(numerator)
print(denominator)
At that point, all the previous tests had passed
Best regards
Well, if the previous tests are good, then your gradient_check logic must be wrong. Here’s what I get with my passing code and your print statements:
4.0000001 3.9999999 8.0000002 7.9999998 2.0000000011677344
2
1.167734353657579e-09
4.000000001167734
Your backward propagation works perfectly fine! difference = 2.919335883291695e-10
Looks like you need to check your logic for computing gradapprox. 
The differencewe have is in gradapprox …
I can’t get it … it’s just simply gradapprox = (theta_plus - theta_minus) / (2.*epsilon)
I wasn’t my logic. It’s a typo in the instructions
I just left epsilon (not 2 * epsilon) as denominator a it worked just fine
Who should I contact to so that this can be ammended on the notebook?
I think you must be mistaken somehow. I did not have this problem.
As Paul pointed out, you did not implement function correctly.
From your post,
gradapprox = (theta_plus - theta_minus) / (epsilon) =
((theta + epsilon) - (theta - epsilon))/epsilon = 2*epsilon/epsion = 2
Your gradapprox is always 2. For this exercise, accidentally, gradapprox =2. So, it can be seen that you passed this test, but actually, not.
Please revisit your implementation. You mixed up theta and J.
Yes, you’re right … and it happened to me in the next functions down the notebook. Thanks for pointing me out my typo …
FYI @paulinpaloalto
Best regards both of you