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# e (Euler's number) explanation, and applications

It is quite well explained here -- https://betterexplained.com/articles/demystifying-the-natural-logarithm-ln/

Although, I don't truly understand, I see it as an attempt to calculate the compound interest curve; and natural logarithms as reverse calculating it.

Feel that this website is about right -- https://betterexplained.com/archives/ (and there are computer science problems, too.)

Though, another approach is to start from problems (thought or real).

BTW, my favorite in computer thingy might be,

``````float Q_rsqrt( float number )
{
long i;
float x2, y;
const float threehalfs = 1.5F;

x2 = number * 0.5F;
y  = number;
i  = * ( long * ) &y;                       // evil floating point bit level hacking
i  = 0x5f3759df - ( i >> 1 );               // what the fuck?
y  = * ( float * ) &i;
y  = y * ( threehalfs - ( x2 * y * y ) );   // 1st iteration
//  y  = y * ( threehalfs - ( x2 * y * y ) );   // 2nd iteration, this can be removed

return y;
}
``````

## Discussion 