Math Help

[speg]

I'm going to sound really dumb in a second, but I haven't taken calculus in 4 years and don't have the textbook with me...

1. For each function below, ?nd
?f and D^2(f)

(a) f (x, y) = x^2 + xy^2 - e^y


I know ? is the grad operator, but what is D^2?

 

[JohnCU]

fuck i aced all my calculus classes but can't remember D^2... ?

 

[josh0099]

2nd derivative?

 

[speg]

I know I've done Calc 3... and this is a "Math for Econ" class, so I haven't been attending most of the classes... it's all pretty easy if only I could understand the question...

 

[chronox]

Could it mean the second derivative of the function f(x,y) via implicit differentiation?

 

[Boo025]

isn't D just differential operator (d/dx)?
http://en.wikipedia.org/wiki/Differential_operator

 

[frostedflakes]

Maybe second derivative of the gradient field? Just a guess, sorry that isn't ringing any bells for me either.

 

[speg]

Originally posted by: Boo025
isn't D just differential operator (d/dx)?
http://en.wikipedia.org/wiki/Differential_operator

I guess so, though we've never used that notation before... and it doesn't specify which variable it is with respect to?

 

[RESmonkey]

Originally posted by: josh0099
2nd derivative?

my guess

 

[Random Variable]

a matrix of all the second order partial derivatives?

 

[MaxFusion16]

it's asking for the second derivative, but with respect to what?
it doesn't specify what variable to differentiate with respect to, x or y.

 

[Random Variable]

.

 

[hypn0tik]

Originally posted by: speg
I'm going to sound really dumb in a second, but I haven't taken calculus in 4 years and don't have the textbook with me...

1. For each function below, ?nd
?f and D^2(f)

(a) f (x, y) = x^2 + xy^2 - e^y


I know ? is the grad operator, but what is D^2?

Is D^2 the Laplacian?

 

[Random Variable]

Originally posted by: hypn0tik

Originally posted by: speg
I'm going to sound really dumb in a second, but I haven't taken calculus in 4 years and don't have the textbook with me...

1. For each function below, ?nd
?f and D^2(f)

(a) f (x, y) = x^2 + xy^2 - e^y


I know ? is the grad operator, but what is D^2?

Is D^2 the Laplacian?

You're probably right.

D(f) = ?f = (?f/?x,?f/?y,?f/?z)
D^2(f) = ?²f = ?·?f = (?/?x,?/?y,?/?z)·(?f/?x,?f/?y,?f/?z) = ?²f/?x²+?²f/?y²+?²f/?z²

 

[TecHNooB]

Originally posted by: Random Variable

Originally posted by: hypn0tik

Originally posted by: speg
I'm going to sound really dumb in a second, but I haven't taken calculus in 4 years and don't have the textbook with me...

1. For each function below, ?nd
?f and D^2(f)

(a) f (x, y) = x^2 + xy^2 - e^y


I know ? is the grad operator, but what is D^2?

Is D^2 the Laplacian?

You're probably right.

D(f) = ?f = (?f/?x,?f/?y,?f/?z)
D^2(f) = ?²f = ?·?f = (?/?x,?/?y,?/?z)·(?f/?x,?f/?y,?f/?z) = ?²f/?x²+?²f/?y²+?²f/?z²

Put those math symbols away!

 

[JohnCU]

Originally posted by: Random Variable

Originally posted by: hypn0tik

Originally posted by: speg
I'm going to sound really dumb in a second, but I haven't taken calculus in 4 years and don't have the textbook with me...

1. For each function below, ?nd
?f and D^2(f)

(a) f (x, y) = x^2 + xy^2 - e^y


I know ? is the grad operator, but what is D^2?

Is D^2 the Laplacian?

You're probably right.

D(f) = ?f = (?f/?x,?f/?y,?f/?z)
D^2(f) = ?²f = ?·?f = (?/?x,?/?y,?/?z)·(?f/?x,?f/?y,?f/?z) = ?²f/?x²+?²f/?y²+?²f/?z²

i just came

 

[chronox]

Originally posted by: JohnCU

Originally posted by: Random Variable

Originally posted by: hypn0tik

Originally posted by: speg
I'm going to sound really dumb in a second, but I haven't taken calculus in 4 years and don't have the textbook with me...

1. For each function below, ?nd
?f and D^2(f)

(a) f (x, y) = x^2 + xy^2 - e^y


I know ? is the grad operator, but what is D^2?

Is D^2 the Laplacian?

You're probably right.

D(f) = ?f = (?f/?x,?f/?y,?f/?z)
D^2(f) = ?²f = ?·?f = (?/?x,?/?y,?/?z)·(?f/?x,?f/?y,?f/?z) = ?²f/?x²+?²f/?y²+?²f/?z²

i just came

:laugh: I've been out of school only 1.5yrs and boy, do I miss seeing this stuff.

 

[artikk]

Originally posted by: JohnCU

Originally posted by: Random Variable

Originally posted by: hypn0tik

Originally posted by: speg
I'm going to sound really dumb in a second, but I haven't taken calculus in 4 years and don't have the textbook with me...

1. For each function below, ?nd
?f and D^2(f)

(a) f (x, y) = x^2 + xy^2 - e^y


I know ? is the grad operator, but what is D^2?

Is D^2 the Laplacian?

You're probably right.

D(f) = ?f = (?f/?x,?f/?y,?f/?z)
D^2(f) = ?²f = ?·?f = (?/?x,?/?y,?/?z)·(?f/?x,?f/?y,?f/?z) = ?²f/?x²+?²f/?y²+?²f/?z²

i just came

lol at this comment, it looks to me to be the derivative of the gradient or 2nd deriv of the multi variable function with respect to each variable

 

[IEC]

I took up to multivariable calc and then promptly forgot most of my calc. Guess this thread inspires me to brush up on some of this again