Recent content by ArnfinnS

thanks for helping. thanks for help. well here is more about my problems : we have Greens Formula I (Pdx + Qdy)=II_omega(dQ/dx - dP/dy)dxdy = I_(boundary of omega) F * dr where the scalar product is supposed to be that it is possible to orthogonal project P on the tangent to Boundary of...

hi..i really need some help. we have that alpha(x,y,x) = 1/r , where r^= x^2 + y^2 + z^2 and where the fector field F = nabla alpha (gradient of alpha) i calculated F to be : (-xx^ + yy^+zz^)/r^3 but iam supposed to calculate the flux integral I_s F*n dS but i don't know how to find...

hi... i need to find the mex and min point of the function f(x,y) = x^2*y*e^(-x^2 - 2y^2) for (x,y) in R^2 here is what i tried : i found the partial derivatives : f_x = 2x*y*e^8-x^2 - 2y^2) + x^2*y*e^(-x^2 -2y^2)*(-2x) and f_y = x^2*y*(-4y)*e^(-x^2 - 2y^2) i see that those partials...

i found that the system has solution at x=y=1/( 2^(0.25)) and x=y=-1/(2^(0.25)) but i also proved that this is a local mininum. and those are the only critical points. how can i prove that its global minimum?

hi. I've got another problem. i have the function : f(x,y) = x^2 + y^2 +(xy)^-1 iam supposed to use the "extremalvalue theorem" to show that this function have a global minimum on the area x>= 0.1 ,y>= 0.1 and i also need to argue if the same thing is satisfied for x>0 and y>0. for...

but how can i prove that it has a global minimum for X>0 and Y>0 ? can someone help me?

yes , but how can i find out which points these partial derivatives is zero? i really can't see which point it is...

hi. I've got another problem. i have the function : f(x,y) = x^2 + y^2 +(xy)^-1 iam supposed to use the "extremalvalue theorem" to show that this function have a global minimum on the area x>= 0.1 ,y>= 0.1 and i also need to argue if the same thing is satisfied for x>0 and y>0. for...

hi yes that's exactly what i meant:) I need to transform the one expression over in the other. Can you help me?

hi yes that's exactly what i meant:) Can you help me?

hi i have a small problem. i need to prove that these two expressions are equal : (n*Sum{i=1,n}Xi*Yi - Sum{i=1,n}Xi*Sum{i=1,n}Yi)/(n*Sum{i=1,n}(Xi)^2 - (Sum{i=1,n}Xi)^2) and the expression : (Sum{i=1,n}(Xi)*(Xi*Y^ - Yi*X^))/(Sum{i=1,n}((Xi)^2 - (x^)^2 )) here is x^ and y^ the...