Hey, Kalid from BetterExplained here, thanks! My general philosophy is to be really, really honest with myself if I understood something. It&#x27;s ok (really!) to admit when we haven&#x27;t fully understood a concept.<p>Want a fun example? How about percentages. Yeah, that thing we mastered in 4th grade or whatever. That thing we use every day.<p>Well, did you know that<p>a% of b = b% of a?<p>Let&#x27;s say you want 16% of 25. Ugh. Ok, let&#x27;s multiply it out... divide by 100... no!<p>How about 25% of 16? Well, that&#x27;s 4. Easy. But are they the same thing?<p>a% of b = a&#x2F;100 * b<p>b% of a = b&#x2F;100 * a<p>Either way, it&#x27;s ab&#x2F;100. Now every percentage problem has a 50% chance of being expressed more easily. How did we miss this? (Argh!!!)<p>Math is full of insights like that. Trig functions (sine, cosine, tan, etc.) are actually themselves percentages. A sine of .95 means you are at 95% of your maximum height (where the max is the hypotenuse). Sine and cosine are unitless numbers, and that&#x27;s why the can be each other&#x27;s derivatives (the percentage change of a percentage change...). So many things click! What else have we overlooked?<p>Anyway, really appreciate the note!