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Feb
25
comment What exactly is the difference between a derivative and a total derivative?
Do you know what the answer was? I keep getting $2r$ even when using Arkamis' formula.
Jan
20
accepted How to deal with x/|x| in an equation?
Jan
19
asked How to deal with x/|x| in an equation?
Sep
23
comment How to take the gradient of the quadratic form?
To help future generations: the full specification of the chain rule used here is $$ \frac{df(g,h)}{dx} = \frac{d(g(x)^T)}{dx} \frac{\partial f(g,h)}{\partial g} + \frac{d(h(x)^T)}{dx} \frac{\partial f(g,h)}{\partial h} $$ The order of multiplication is very important since we're dealing with vectors!
Sep
12
comment Texbook with proof that product of two Gaussian functions is also Gaussian
Unfortunately John's blog post doesn't contain the full derivation. Would anyone like to contribute a line-by-line proof? Or cite a textbook that has one?
Dec
2
comment What exactly is the difference between a derivative and a total derivative?
OP: Did they say that your answer was wrong, or only that you solved it using the wrong method?
Jun
20
awarded  Autobiographer
Mar
27
awarded  Student
Mar
27
awarded  Scholar
Mar
27
awarded  Editor
Mar
27
comment How is it that some forms of an equation can have a defined outcome while other forms of the same equation are undefined?
Thinking back, I now realize that I've tripped over this problem again and again when evaluating algebraic expressions. Are there some basic rules to keep in mind to stop me from making illegal steps?? Or would I have to study this whole branch of mathematics to know the difference? :-P
Mar
27
accepted How is it that some forms of an equation can have a defined outcome while other forms of the same equation are undefined?
Mar
27
revised How is it that some forms of an equation can have a defined outcome while other forms of the same equation are undefined?
added 107 characters in body
Mar
27
asked How is it that some forms of an equation can have a defined outcome while other forms of the same equation are undefined?
Jan
2
awarded  Supporter