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Yeah, usually they don't explain the "why"s (and going through the effort of trying to understand it is usually not rewarded in the exam, due to the nature of questions asked etc.).

What is the main reason you think it sucks? (:haha:)

Because of the Law of Conservation of Momentum (and Newton's Third Law). Because of Newton's Third Law.

It's pretty different. Most of Prelim Chemistry knowledge is irrelevant for HSC Chemistry. Different people have different preferences of Prelim vs. HSC Chemistry.

With gravity, it instead becomes mg.sin(θ), where m is the mass of the car. (But yes, technically gravity isn't the force (I think), but rather the cause of a force; we should say "force due to gravity", aka weight.)

My Riemann zeta query was in reference to your "do you know that the Riemann Zeta function WAS actually examined in the HSC in 1975" comment. Anyway, I had a look back at buchanan's old post (http://community.boredofstudies.org/238/extracurricular-topics/102519/arc-length.html#post2220688) about...

Lol.

The Riemann zeta function was in the HSC syllabus before, right?

The dividing by the derivative of tan(x) won't work because tan(x) isn't a linear function. We can only generally do this (divide by the derivative of the function) if that function is linear (ax+b (a non-zero)).

$\noindent Reverse chain rule after the substitution you mean? It ends up becoming $\int \frac{2u^2}{1+u^4}\text{ d}u,$ where $u=\sqrt{\tan x}$. This doesn't lend itself to an immediate reverse chain rule.$ $\noindent If you want further tedium, you can try integrals of $\sqrt[3]{\tan x}$...

I think the wording of the original post was the main reason for lots of posting of "joke" questions. (Original post: )

The typical HSC Conics Q. is mainly tedious algebra.

Well, looks like DatAtarLyfe and his friend got it out in a double period! (Just kidding, he's referring to the integral. :haha:)

Re: HSC 2016 2U Marathon Here's another Q about averages. $\noindent Let $n$ be an integer greater than $1$ and let $x_1,x_2,\ldots , x_n$ be $n$ real numbers. Let $w_1,w_2,\ldots , w_n$ be $n$ real numbers satisfying $w_i \geq 0$ for all $i$ and $\sum _{i=1} ^{n} w_i = 1$. Let $WA = \sum...

I assume by 'percent' it means percentage of 200 g, since the 200 mL of water will be essentially 200 g. So you'll need to add: 4 g, 20 g, 40 g, respectively. The formula for x% of y is that x% of y equals xy/100.

Re: HSC 2016 2U Marathon Raise e to the power of both sides, then ln(x) = e. Hence x = ee.

Re: HSC 2016 2U Marathon Btw, expressions like f(x+1) - f(x) are known as finite forward differences (see here for more info: https://en.wikipedia.org/wiki/Finite_difference ). They can be used to approximate derivatives to help solve (numerically) differential equations. From the series and...

Re: HSC 2016 2U Marathon Pretty much. Like the main thing to say was that f'(x) can be calculated just using the gradient formula, which I think you said at the end.

Re: HSC 2016 2U Marathon Well done! Yeah, for the second one, the slope of the line is just [f(x+1) - f(x)]/[(x+1) - x] = f(x+1) - f(x), explaining why f'(x) comes out to be f(x+1) - f(x) (or we could've used any other place, like f(t+1) - f(t) for any real t, since the slope is constant).

Yes. I believe the laws of physics as we know them break down there.