Recent content by Raffaele

I wonder why electromagnetic waves don't escape from a black hole while gravitational waves (obviously) do. What is the difference between the two kind of waves? And between gravitons and photons? thank you for your attention

<Moderator's note: Moved from a technical forum and thus no template.> My daughter, who attends the italian equivalent of US K9, asked me some advice about a physics hydrostatic problem. > Which pressure (in atmospheres) a fireman must use to send water at 12 > meters height. I tried to use...

I noticed that for any integer greater than 4 there exists at least one perfect square in the open interval (n, 2n). I think I have proved the statement, but as I am not a professional, I'd like someone to review my proof. By induction we see that it is true for n=5 because 5<9<10. Now suppose...

Incenter is the intersection point of bisector lines of the angles of the triangle Circumcenter is the intersection point of the sides perpendicular bisectors Ortocenter is the intersection point of the height Centroid is the intersection point of the medians The average of the coordinates...

I totally agree. By the fundamental theorem of algebra an equation P_n(z)=a_0+a_1z+\ldots+a_nz^n=0 has at least a solution in the complex field \mathbb{C} z_1=a+bi So the LHS of the equation above can be written as (z-z_1)P_{n-1}(z)=0 we can repeat the previous step up to n times getting n roots...

You can get \vec{AB} instantly as \vec{AB}=\vec{OB}-\vec{OA}=(3-2)\vec{i}+(-1-6)\vec{j}+(-2-0)\vec{k}=\vec{i}-7\vec{j}-2\vec{k} gradient of \vec{AB} means null vector, as \vec{AB} is constant. Maybe you wanted the module, the norm ||\vec{AB}||=\sqrt{1^2+(-7)^2+(-2)^2}=\sqrt{54}=3\sqrt{6}