# Thread: davidgoes4wce Useful Maths Questions & Textbook Errata 2017

1. ## davidgoes4wce Useful Maths Questions & Textbook Errata 2017

This question from A T A R Notes.com by Jacob Silove is confusing. There is no mention of what course Jacob studied and it's the first time I have ever heard of him.

Here is an excerpt:

Could have better worded it along the lines of:

"Find the equation of the line that is perpendicular to 2x+5y=12, that goes through the point (3,5). Then find out what y-value which corresponds to when x=-3. "

When doing this question first up, I initially thought it was the intersection of x=-3 with the line 2x+5y=12 and determining the perpendicular gradient and equation from there.

Done a lot of calculus questions but personally no a fan of his wording of the question.

I think he should have worded the question a lot better.

2. ## Re: HSC 2017 Maths (Advanced) Marathon

Question seems complicated, but is not.

But let point A be (-3,b). The given line has gradient -(2/5). Therefore gradient of AB is 5/2.

Since B is (3,5), gradient of AB being (5-b)/(3+3) = 5/2. It follows b = -10

i.e the required point A is (-3,-10)

Silove's solution rather long-winded and is harder than necessary. You don't need the equation of AB.

3. ## Re: HSC 2017 Maths (Advanced) Marathon

Jacob Silove in A T A R Notes.com, in his last line and third last line contradict himself. He says angle APB in one instance is 26 degrees and the last line is 38 degrees. Angle APB should be 26 degrees. (sum of angles in APX is a triangle)

Also correct me if Im wrong but the way he has drawn triangle ABC , AC looks a tad longer in length than side AB.

4. ## Re: HSC 2017 Maths (Advanced) Marathon

The specs are incomplete. So angle ABP is undefined. Try drawing same diagram with AB twice its current length (whatever this is) - you obtain a different angle ABP. The fact questions of this type tend to deliberately distort the actual dimensions does not help.

What I'm trying to say is: you can draw an infinite number of diagrams satisfying the specs as it stands. For someone who recently completed his HSC (ATAR: 99.80), Silove's maths isn't bad but has room for improvement. I salute him though for being able to produce such professional-looking material and for being so enterprising.

5. ## Re: HSC 2017 Maths (Advanced) Marathon

Jacob Silove made another mistake which is important to 2017 HSC students.

The last line of description of the asymptote is wrong.

It should be

$lim_{x \rightarrow 1^{+}} \frac{1}{x-1} = \infty$

Jacob missed the positive sign .

6. ## Re: davidgoes4wce Useful Maths Questions & Textbook Errata 2017

2 more mistakes from Silove's notes:

It should be worded:

$The standard cos graph has a period of 2 \pi. The graph of y=cos (\frac{x}{2}) has a period of 4 \pi$

7. ## Re: davidgoes4wce Useful Maths Questions & Textbook Errata 2017

This is the working out for the first question

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