Feb
19
answered Find sum of roots of complex equation $z^6 = z^{18} = -1$
Feb
17
answered Relation betwen coefficients and roots of a polynomial, K.A.Stroud
Feb
17
comment Grandi's series contradiction
no, it is not a contradicition. closed under addition means that any finite sum of integer is an integer. Are you talking about finite sums of integers? What are you talking about? It is a contradiction of you say $S=0$ and $S=1$ because the numbers $0$ and $1$ are different in $\mathbb{Z}$
Feb
17
comment Regions in $\mathbb{C}$ containing rectangles
@5xum No, if $\Omega$ is the rectangle $1,i,-1,-1$ an the right triangle is $0.9, 0, 0.9i$ the 4th vertex is $0.9+0.9i$ which is not in $\Omega$
Feb
17
comment Regions in $\mathbb{C}$ containing rectangles
@Marcin Łoś No, if $\Omega$ is the rectangle $1,i,-1,-1$ an the right triangle is $0.9, 0, 0.9i$ the 4th vertex is $0.9+0.9i$ which is not in $\Omega$
Feb
17
comment Regions in $\mathbb{C}$ containing rectangles
So it is not necessary for $\Omega$ to be connected?
Feb
16
comment probability $2/4$ vs $3/6$
@Thomas Ahle is the question unintuitive or the answer?
Feb
16
comment Tricks. If $\{x_n\}$ converges, then Cesaro Mean converges (S.A. pp 50 2.3.11)
What is the meaning of S.A. int the title?
Feb
16
comment Tricky positive diophantine equation
Where have you found this problem?
Feb
14
comment Non-zero prime ideals of $F[x]$ are maximal
all posters have questions about something. something like "ideals of $F[X]$" would be a more meaningful title
Feb
13
comment Finding the zeros of a polynomial equation.
here an example of calculationg the root with Cardanos formula. But this is rather labourious. Maybe there is a typo in the equation? You can find the exact solution using a CAS like Wolfram Alpha.
Feb
13
comment Finding the area of a circle given the inscribed figure inside it
yes, I see this now.
Feb
13
comment Finding the area of a circle given the inscribed figure inside it
I think this is simpler. If we arrange the triangles in this alternating manner and call the vertexes of the hexagon $A,B,\ldots,F$ then $A,C,E$ is an equilateral triangle with $AC=\sqrt{3}r$. $M$ is the center of the circle and $\angle(A,M,C)=\frac{2 \pi}{3}$ and so $\angle(A,B,C)=\frac{2 \pi}{3}$. Using the law of cosine we get ${AC}^2=1^2+2^2-2 \cdot 1 \cdot 2 \cdot \cos{\frac{2 \pi}{3}}=7$. So $3r^2=7$
Feb
13
answered Finding the area of a circle given the inscribed figure inside it
Feb
12
revised Function F(x,y) which is high when (both x and y are high) and (x is close to y)
grammar
Feb
12
comment If a is an arbitrary integer, then 6|a(a^2+11)
using Maxima makelist(mod(a*(a^2+11),6),a,0,5); gives [0,0,0,0,0,0]
Feb
10
comment Show that $x^4 + 8$ is irreducible over Z
@neofoxmulder No, he picked $x=9$ for the polynomial $x^4+8$ because $9$ is greater than all coefficients of the polynom. Also the coefficients have to be not negative to apply Cohn's test. For the polynomial $x^3+1$ you have to select an $x \ge 2$ for Cohn's test.
Feb
9
answered How to quickly find $\sqrt{x^4+4x^3+2x^2-4x+1}$ or anything similar
Feb
3
revised Gateaux Derivative.
correct log function in latex
Feb
3
comment proving zeros of a polynomial are not real
see math.stackexchange.com/questions/494243/… there I use Sturm's theorem to show this. This method is straightforward and is implemented in some CAS (e.g. Maxima) to find the numbers of real roots in an interval