# Recent content by Mappe

1. ### Complex derivative and div/curl

In trying to get an intuition for curl and divergence, Ive understood that in the case of R2, div f(x,y) = 2Re( d/dz f(z,z_)) and curl f(x,y) = 2Im( d/dz f(z,z_)), where f(z,z_) is just f(x,y) expressed in z and z conjugate (z_). Is there any way of proving the fundamental properties of div and...
2. ### Using complex description of div and curl in 2d?

some characters did not write out, f(z,z_) its supposed to say, with z_ being complex conjugate
3. ### Using complex description of div and curl in 2d?

In trying to get an intuition for curl and divergence, Ive understood that in the case of R2, div f(x,y) = 2Re( d/dz f(z,z_)) and curl f(x,y) = 2Im( d/dz f(z,z)), where f(z,z) is just f(x,y) expressed in z and z conjugate (z). Is there any way of proving the fundamental properties of div and...
4. ### Tools to analyze sequences

I need the math tools to understand and analyze sequences and their convergence. I know for example that the fibonacci series can be rewritten such that we can calculate for example nr 153 without knowledge of previous numbers. What math subjects is needed to take care of more complicated...

General relation I meant off cause ;\

Is there a general between the eigenvectors of a matrix and the row (or column) vectors making up the matrix?
7. ### Simplify the proof of different vector calculus identities

Im talking about all these identities, is there a branch of mathematics that simplifies the proofs of these, and lets me avoid expending the vectors and del operators?
8. ### Simplify the proof of different vector calculus identities

Is there a way to simplify the proof of different vecot calculus identities, such as grad of f*g, which is expandable. And also curl of the curl of a field. Is there a more convenient way to go about proving these relations than to go through the long calculations of actually performing the curl...
9. ### Making sense of vector derivatives

Im trying to understand helmholts decomposition, and in order to do so, I feel the need to understand the different ways to apply the del operator to a vector valued function. The dot product and the cross product between two ordinary vectors are easy to understand, thinking about them as a...
10. ### Motivation of sin and cos functions

Is there a way to motivate the sinus and cosinus functions by looking at their Taylor expansion? Or equivalently, is there a way to see that complex numbers adds their angles when multiplied without knowledge of sin and cos?
11. ### Mathematical insight about waves

Dr Courtney, I understand but your statement implies that we know that e-i2π = 1, and from the definition of eix by its taylor expansion, how can we see on its derivatives that its gonna be periodic and perhaps also how do we see from this definition that it describes a circle? The same question...
12. ### Mathematical insight about waves

I want to have a simple and intuitive explanation of why the sin and cos waves have such a simple repetitive values for their derivatives at a specific point. Their derivative values are also periodic in respect to the derivative order. For example, e^-x is also periodic, but its derivatives are...
13. ### Holomorphic functions

Yes, I know about that condition, but how does that imply that the derivate value in one point is independent of the direction in which it is approached? What does being continuously differentiable have to do with that?
14. ### Holomorphic functions

I was told an analytic complex functions has the same derivation value at z0 (random point) however you approach z0. The cauchy riemann eq. shows that z0 has the same derivate value from 2 directions, perpendicular to each other. However, at least some real functions can have the same derivate...
15. ### Sturm Liouville problems

Thanx, but I meant to integrate the legendre with another function, <f,P(n)>, the inner product. My function is x^2, so the integral/inner product will be <x^2,P(n)>, to find the coefficients for a series-expression of x^2 with legendre as the base.