Standard Math Q+A Thread

[samsclaire]

hey! can someone please explain trig with obtuse angles? (i really don't get how it works)

[S200]

Got an example question??

[jakesilove]

hey! can someone please explain trig with obtuse angles? (i really don't get how it works)

Hey! I didn't do General, but I'm using your formula sheet as a guide. Let's look at the following triangle

We denote capital letters as the angle, and small letters as the side. There are a few formulas you need to know
Area

First, you need to be able to find the area of this triangle. To do this, we simply apply the formula

Note that the angle, C, needs to be between the two sides a and b. So, in the above triangle, the formula would actually be

You only need to know one angle, and the two sides surrounding that angle, to get the area!



The sine rule states that the ratio of the sine of an angle over the opposite side is the same as the ratio of the sine of any other angle over their opposite sides. On your formula sheet, it is

In our above triangle, it will be


Note that it's all about the ANGLE and it's OPPOSITE side! Here, you can use two known angles and a known side to find other sides, or two known sides and one known angle to find another angle.

Cosine rule

Finally, we have the cosine rule, which is used to find angles or sides given known values. On your formula sheet, the rule is




Give us some example questions we can help you with! It'll be way easier to understand when you're applying it

[Lachlan Morley]

Does anyone have any tips to ensure that silly mistake in exams are eradicated, normally I know how to do the question although i miss out a key part of the question

[RuiAce]

Does anyone have any tips to ensure that silly mistake in exams are eradicated, normally I know how to do the question although i miss out a key part of the question

Eradicating it is hard. People that eradicate silly mistakes are the ones that get state ranks.

Of course, that's definitely possible. But setting goals that high is asking quite far. Let's think about how you can minimise it. In the HSC, you're allowed to take a highlighter in with you. You can use this to your advantage in one of two ways:
- Highlight everything that's likely to important, and preferably use two highlighters so you can contrast between the two. This will definitely include numbers and any variables given.
- Highlight things as they get used, and consider when and how you used them.
As usual, underlining is a substitute if you can make it effective.

Read the question twice. Scan the text to know what's going on (and look at diagrams/tables given at the same time to relate what you read). Look out for some key words like tax, interquartile range etc.

The examiners aren't going to look at your multiple choice question booklet. You can use that as scrap paper. You can list out the things you're looking for as you're going through the questions. (Of course, can understand why this might be time consuming.)

There's quite a ton of topics in maths, so in your free time it may help to list out where the silly mistakes tend to be within specific topics. Then, when doing past papers and what not, have those lists out in front of you so you can check to see what you might miss out on. Same goes for questions in general (e.g. misreading a key word). Having a list of silly mistakes out in front of you and being able to check it as you're studying will help you ensure that you won't make such mistakes on the day.

[sageziman]

Would anyone be able to break down the working out for 10 b and c for me please

[RuiAce]

Would anyone be able to break down the working out for 10 b and c for me please

To ensure that we have exactly one ace, we put that in first. Note that there are 4 aces, so we have 4 possible outcomes.

For the other cards, treat it like part a) except we only have 48 cards and not 52 to consider now. Remember, we don't want any more aces.
Similar to part a), I.e. Factoring in repetition, we have 48*47*46*45/4!

So the answer is 4*48*47*46*45/4!

Part c is similar but there's repetition in the aces as well because now we want exactly two aces. I leave you to think about why the answer is 4*3/2! times 48*47*46/3! using a similar analysis

[lilmisshemingway]

Hi anyone/everyone!
I just got a sighted task back for General Maths and I failed. Like, really badly failed. I've had a 45-50% average for this subject this entire year, and I've been a little slack on homework because of competing priorities and math tends to get pushed to the side because of my 4u Major Work. I've always had a really negative mindset surrounding maths-- and I'm on 11 units so I can't drop, and half of it is going to count towards my ATAR whether I like it or not.
So is it possible that I can still pick up my marks for trials and HSC? I really don't want to end up with a Band 3. 

[S200]

Hi anyone/everyone!
I just got a sighted task back for General Maths and I failed. Like, really badly failed. I've had a 45-50% average for this subject this entire year, and I've been a little slack on homework because of competing priorities and math tends to get pushed to the side because of my 4u Major Work. I've always had a really negative mindset surrounding maths-- and I'm on 11 units so I can't drop, and half of it is going to count towards my ATAR whether I like it or not.
So is it possible that I can still pick up my marks for trials and HSC? I really don't want to end up with a Band 3. 

Hey there!!
You think THAT's a fail??
My teacher told me last week, just before my exam, that I had failed my re-sit of my Methods Sac... so thats an N for the semester...
Other than moral support, my only advice I can give is the same as I'm doing right now...
Bed @ 10, awake at 4.30, get onto the homework!!
Catch up or else!!

"The good thing about hitting rock bottom??... There's only one way you can go!! And thats UP!!!

[emilybrooks99]

I've got my maths trial exam tomorrow and I'm doing last minute revision and review tests from my textbook. Can anyone help me with getting the answers for 14 and 15 cause nothing I seem to do matches up with the answers in the back of the book

[RuiAce]

I've got my maths trial exam tomorrow and I'm doing last minute revision and review tests from my textbook. Can anyone help me with getting the answers for 14 and 15 cause nothing I seem to do matches up with the answers in the back of the book

(Image removed from quote.)

____________________________



Divide to get C.

[olr1999]

Best way to pick up silly mistakes?

[jamonwindeyer]

Best way to pick up silly mistakes?

Hey! Didn't do General, but I feel like spotting mistakes works the same at any level of Maths study! You'll want to make sure you are moving slowly through the exam (within reason of course). Highlight key terms, put things into your calculator properly and carefully - Try to avoid making the mistake in the first place. Beyond that, to pick up a silly mistake you need to know the ones you usually make. Are you likely to make a mistake in algebra? Try double checking algebra working in the last five minutes. Screw up the interest rate in Credit Card questions? Take 30 seconds to check yourself before you move on from those questions.

You know the saying, "Know your enemy?" That's exactly my advice here

[olr1999]

Hey! Didn't do General, but I feel like spotting mistakes works the same at any level of Maths study! You'll want to make sure you are moving slowly through the exam (within reason of course). Highlight key terms, put things into your calculator properly and carefully - Try to avoid making the mistake in the first place. Beyond that, to pick up a silly mistake you need to know the ones you usually make. Are you likely to make a mistake in algebra? Try double checking algebra working in the last five minutes. Screw up the interest rate in Credit Card questions? Take 30 seconds to check yourself before you move on from those questions.

You know the saying, "Know your enemy?" That's exactly my advice here

Awesome! Thanks so much

[morning_sunshine]

Hi all

So I am currently prepping for my general maths exam and am stuck on this question. Any help would be appreciated.

Josephine invested $1000 at the end of each year for five years. Her investment earned interest at 4.8% per annum compounded annually. What was the total of Jospehine's investment (to the nearest dollar) at the end of the fifth year?

Thanks