 FChaosi_

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1. Tense is not in the criteria. It does not matter at all.
2. How to recognize which double angle formula to use?

Well, you want cos B, not cos (2B), so of course you'll use the first one, which only requires you to know sin B.
3. 1) The first thing to notice is that we can essentially ignore what the cost is, because the cost is is minimised when the total surface area of the box is minimised. The next thing to notice is that our area function will be of the following form: A(x) = (1 + 1/3)*A(top) + (1 + 1/3)*A(front) + 2*A(side) This is simply because the cost of an oak piece is exactly three times the cost of a pine piece with the same area. Let x be the shortest side of the base (and hence the longer side is 2x). So, A(base) = 2x^2. We can find the height, h, because: 12.25 = h*A(base) h = 12.25/(2x^2) = 6.125/x^2 Hence A(x) becomes: A(x) = 4/3[2x^2] + 4/3[x*6.125/x^2] + 2[2x*6.125/x^2] Simplifying, A(x) = (2/3)x^2 + [49/(6x)] + [49/(2x)] A(x) is minimized where A'(x) = 0. Using a calculator, because differentiating by hand is gonna result in messy fractions, yields a minimum for the area (and so a minumum for the cost) when x = 2.90 dm, to 3 significant figures. So that's the shortest side, the longest side is 2*2.90 = 5.8 dm, and the height is 0.728 dm. That was a pretty fun problem. Working on 2).
4. u4/u1 = r^3 r^3 = [1/3]/[1/81] r^3 = 27 r = 3 Graph Sn using sum of a geometric series formula. Find Sn = 40 using graphics calculator. Given that Sn increases as n increases, round to the next n if needed.
5. Don't listen to people who say you're crazy. Do what you love. It's doable.
6. chemistryhl Does ethyl ethanoate dissolve in water and do they form hydrogen bonds (intra // inter ) ?

It's fairly soluble in water, because although it has hydrocarbon components - namely the C-H bonds - it also has an ester functional group, which is polar and can hydrogen bond with water. The oxygen atoms in ethyl ethanoate can form hydrogen bonds with hydrogen atoms in water molecules, but the hydrogen atoms in ethyl ethanoate cannot form hydrogen bonds with the oxygen atoms in water molecules.
7. Stricly, Hess's Law involves multiple reactions. For each substance listed in the question, there is only one reaction, so Hess's Law isn't needed. You can just use the equation: Q = mcΔt The specific heat capacity is given, as are the masses and changes in temperature, so all you have to do is plug in the values and compare the heat produced. By the way, the heat produced will be the negative of Q, as Q is the energy taken in by the environment.
8. Exams are less than two weeks away now, so how ready is everyone? I still have to do past papers for three subjects but I'm feeling pretty good about the other three. Ehh, that's a lie; I'm worried about all my subjects...
9. Hello, I recently uploaded a draft of my chemistry IA for my teacher to give limited feedback (as he is not allowed to directly tell us what went wrong). I wrote 13 pages and believe my content is of high quality, however, I am still paranoid because most of the chemistry involved with my discussion and evaluation of my results comes from a discussion between a chemistry professor and I on the site www.reddit.com. I am fairly certain that he is who he claims he is through my conversations with him and I am sure that he will provide photos/documents as evidence of his identity if I asked for them. Still I am afraid that this does not count as valid resources. My friend tells me that I will be fine and it's only a draft but this friend has also mixed up the demand and supply curve multiple times in his 2nd years of HL economics. Will I be okay? Or will I have to rewrite my discussion/evaluation with a more credible source?
10. I totally understand your viewpoint. English Lit is my weakest subject for sure, and I'm a logic person too. I think it's a little unfair that subjects like ESS and Maths Studies exist - basically "easy" versions of the maths and science subjects - whereas literature is compulsory. (It's compulsory at my school at least). Sure, people might struggle with science or math but if they can take it at an easier level, why can't the same be done for literature? But throughout IB, I must say, my understanding of literature has developed a lot, and with that so has my respect for it. Just as you appreciate music for its sound and its meaning, literature is an art form that expresses the human condition. You're still at the start of IB, so just because you don't "get" literature now, it doesn't mean you can't "get" it at all. I think you should put effort into your literature class, and who knows, you might start liking the books/poems you look at as you get a deeper understanding of them, and what they mean.
11. Chemistry: https://ibpublishing.ibo.org/server2/rest/app/tsm.xql?doc=d_4_chemi_tsm_1408_1_e&part=6&chapter=1 Biology: https://ibpublishing.ibo.org/server2/rest/app/tsm.xql?doc=d_4_biolo_tsm_1408_1_e&part=6&chapter=1 Physics: https://ibpublishing.ibo.org/server2/rest/app/tsm.xql?doc=d_4_physi_tsm_1408_1_e&part=6&chapter=1 They are listed under "prescribed practicals".
12. According to the 2016 syllabus they are called domains of life, and there are 3:
13. The Haese one may seem much bigger than the others, but that's because it has such in-depth explanations. The Haese book is very good.
14. Hi hi hi. I take all of those subjects, and at higher level, except Biology at standard level. Maths HL is a ton of work but if you're doing well now you will be okay. Chemistry HL is notorious for being one of the hardest subjects in IB, but it's honestly not that bad, provided you do all the work. Biology is a bit different from these two in that it's almost straight memorization. Biology HL particuarly is a lot to remember. If you're not a memory person, I wouldn't take Biology HL if you want to maximize your IB score. Like, it's doable, you can take Biology HL and get a 7, but it will take a lot of your time. Biology SL has a lot less content so is much "easier". Economics is kind of in between being a memorization and application subject, since you write a lot of essays but you also need to be able to use concepts. Economics HL is very easy: the content is not hard, and the only thing additional you do at HL rather than SL is perform basic calculations, no more complex than linear equations. So overall, I take these subjects, but Bio at SL, and I'm fine, so you should be too, if you are willing to put in the time for Bio HL, and do all of your homework.
15. Yes you can. Your option exam paper will contain questions for all the options, and you can pick which option you'll answer the questions for.
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