I have a simple question about the formula for the volume of the cone. Let $C$ a cone, which base has radius $r$ and height equal to $h$. So its volume can be compute by the formula:  $$\text{Vol}(C)=\frac{\pi r^2h}{3}; $$ so far nothing new. I know how to deduce this formula using the integral, but:   why is the volume of the cone exactly one third of the volume of a cylinder with same circle base and the same height? I'm looking for a way to see it without using integral.
The volume of a cone with height $h$ and radius $r$ is $\frac{1}{3} \pi r^2 h$, which is exactly one third the volume of the smallest cylinder that it fits inside.  This can be proved easily by considering a cone as a , but I would like to know if it can be proved or at least visual demonstrated without using calculus.
Is it bad to use a pacifier? I've been using it when she gets fussy and she seems to love it. Is this a bad habit to get into? I've heard there are potential dental/breastfeeding/dependency issues. Is there any truth to this? Why do all SSH-RSA Keys begin with "AAAAB3NzaC1yc"? Does Moore's law apply to quantum computing? Plain and simple. Does  apply to quantum computing, or is it similar but with the numbers adjusted (ex. triples every 2 years). Also, if Moore's law doesn't apply, why do qubits change it? If someone else is booking international ticket for me using his credit or debit card, does he need to be present physically at the time of check-in?   Suppose I am coming back from Singapore to my home country and my ticket is booked by my friend for me, who lives in my home country. Do airlines in Singapore ask for the person to be present physically to check in? I want to create a wave made out of particles/dots. The wave should look like this:  I tried to achieve this effect by adding an ocean modifier to a plane. Then I added a particle system to the plane but now I don't know how to go on. How can I make the particles lay on the 'ocean' and move when the ocean is moving? PS: I know there is a way to do this with a material in the Blender Render. But firstly I want to create the whole thing in Cycles and secondly I want to have particles. Why are hard drives never as large as advertised? From all the hard drives I have bought, they never seem to be as large as the advertised size; from 320 GB down to 290 GB, from 500 GB down to 450 GB, etc. Is there a technical reason for this? How to read from two input files using while loop Dictionary for TeXstudio: “No dictionary Available” I have trouble spell checking my document in TeXstudio. When I press spellcheck, I get the error No dictionary Available. Am I supposed to install a dictionary separately? How? Any suggestion? How to run test methods in specific order in JUnit4? I'm trying to install wifi drivers for a particular mini wifi card i bought. The output of lsusb is:  0bda:f179 Realtek Semiconductor Corp   I've searched everywhere for drivers, but could not find anything. Any help?  Thanks What is a good Hash function? I saw a lot of hash function and applications in my data structures courses in college, but I mostly got that it's pretty hard to make a good hash function. As a rule of thumb to avoid collisions my professor said that:  function Hash(key)   return key mod PrimeNumber end   (mod is the % operator in C and similar languages)  with the prime number to be the size of the hash table. I get that is a somewhat good function to avoid collisions and a fast one, but how can I make a better one? Is there better hash functions for string keys against numeric keys? Change date format [YYYYMMDD] to [MM/DD/YYYY] I generated a report that formats date as 20160509 and my Google Sheets locale is already set to United States. I've played around with various options within Format > Number > Date Format but I can't change the dates to MM/DD/YYYY format without doing a simple find and replace. How do I accomplish this? I'm working under 12.04 and suppose I have a Firefox windows active (or in foreground) with English as input language and I need to type a document in other language using some text editor.   With the text editor in foreground (or active) and the input language set to a non-English one, when I bring Firefox in foreground (or making it active) the input language remains set to the non-English and the language flag does not switch to English (as it would be expected, since I do not alter the language during the whole Firefox session).  Because of this, I have to make extra moves and change the input language manually every time I switch from the text editor to Firefox and back to text editor. This was not happening with 10.04, and each application windows had the corresponding input language set to its default or previous session every time I was bringing it to the foreground!   How will I make 12.04 to behave the same way? Windows 7 unidentified network (or limited access) after hibernate My windows 7 network will show limited access or unidentified network after coming up from hibernation.  In the office I normally use LAN connection, I turn-off my wireless card (DELL Latitude has on/off switch for the wireless card). When I back at home I will turn on the wireless card, but it will take about 15 seconds to detect my home WIFI and then show limited access. I will have to restart the notebook and it will be able to connect to my WIFI and internet.  The problem will be solved if I restart the notebook, but that defeats the purpose of hibernation doesn't it?  I have tried uninstalling the wireless card driver but still does not solve it. I also tried updating my network card driver but windows says I am using the latest driver. On support.dell.com also showing I am using the latest driver. I understand that information cannot be transmitted at a velocity greater than speed of light. I think of this in terms of the radio broadcast: the station sends out carrier frequencies $\omega_c$ but the actual content is carried in the modulated wave, the sidebands $\omega_c\pm\omega_m$. The modulation envelop has its group velocity and this is the speed at which information is being transmitted. We also know, for example, that x-rays in glass have a phase velocity which is greater than the speed of light in vacuum.   My question is, what exactly is it that is travelling faster than the speed of light?    EDIT: I know it couldn't be anything physical as its superluminal. My problem is, what is it that has absolutely no information content yet we associate a velocity with it. PHP script not executing on Apache server How to install Opera Browser? I am trying to install opera browser from the terminal.  I downloaded the 'debian' installer because it didn't show up in software center.  It completely destroyed my software center - it is frozen and I have no idea how to fix (I have a different thread for that though).  Can I use this thing called synaptic package manager to install Opera?  or am I stuck with Firefox?    How do I install Opera Browser? Blender 2.8 : python code to switch shading mode (between wireframe and solid mode) If i switch between solid and wireframe mode, i can see in the info window that these commands are invoked :  bpy.data.screens["Layout"].shading.type = 'WIREFRAME' bpy.data.screens["Layout"].shading.type = 'SOLID'   Now i want to execute this command using python console. So i cut and paste the codes into python console but i got this error :   &gt;&gt;&gt; bpy.data.screens["Layout"].shading.type = 'WIREFRAME' Traceback (most recent call last):   File "&lt;blender_console&gt;", line 1, in &lt;module&gt; AttributeError: 'Screen' object has no attribute 'shading'  &gt;&gt;&gt; bpy.data.screens["Layout"].shading.type = 'SOLID' Traceback (most recent call last):   File "&lt;blender_console&gt;", line 1, in &lt;module&gt; AttributeError: 'Screen' object has no attribute 'shading'   Does anyone know why ? and what the correct script should i use in python console ?  Thanks PHP & MySQL: mysqli_num_rows() expects parameter 1 to be mysqli_result, boolean given Why can Naruto still use Rasenshuriken?