markvp

This is a math riddle I once made up myself, and stunned several people:

What is the integral of arctan(arctan(x+1)) - arctan(arctan(x-1)) from -∞ to +∞ ?

There is an easy way to do this, only a few lines of simple calculus.

There are infinitely many prime numbers. Proof: suppose there was a finite number of prime numbers. Multiply them and add one. This number is not divisible by any of the prime numbers we have. So this number is another prime or can be factored into other prime numbers, so our supposition is wrong.

Making a joke about this is left as an exercise to the reader.

I have an account with Saxobank to invest. I have tried a few times to buy USLV (from Credit Suisse), but I always get the error message "Exposure cannot be increased due to instrument configuration".

I have no idea what this means, does it mean that I have to change a configuration for this type of product, or did Saxobank configure this product? I have no other open trades, and I want to buy an amount of USLV that is less than the money in my account, so my exposure should not be too big. I traded USLV several times in the past without any problems.

I contacted their support, but after a week I still didn't get an answer!

Hi everyone,

What would be the best way to classify sounds? I only need to know if a sound is of one particular kind or not, e.g. drums or not, so slamming a locker and gunshots should not be in the category.

I was thinking about using the spectrum and feed the amplitudes, or the average amplitude of every octave, to a logistic regression. Are there better ways?

What would be the best way to discriminate between explosive sounds, like slamming a locker, a kick drum and a gunshot? I don't know when the sound starts, but that could be easily done by detecting a sudden amplitude change.

My best guess is a machine learning algorithm that works on the spectrum, e.g. logistic regression.

A few weeks ago I registered a demo account with IronFX. Yesterday I received an email from them informing me that this month they offer a 100% bonus on your first deposit, up to $4000, and also on a redeposit up to $2000.

Is this too good to be true? How could they afford to offer that much money? And are there other brokers who do this?

I'm looking for hourly exchange rates (or even minutes) of the major pairs, that can be downloaded (e.g. CSV, no charts). Preferably of the last 6 months. I tried several of the sites in the sidebar of r/Forex, but no luck, neither on OANDA where I found great daily rates.

Any ideas?

Crash course is a Youtube channel that posts a new video every week on both world history and biology.