# astonky

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• Exams
May 2018
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Germany
1. ## Trigonometry question: sine and cosine

Hi, For my homework, I need to solve the following question: Given that cos a = 4/5 and cos b = 7/25, find the possible values of cos (a+b). What I have done so far is this: Using compound angle identites: cos (a+b) = cos a cos b - sin a sin b Therefore: cos (a+b) = (4/5)*(7/25) - sin a sin b I now used a calculator to find the values of cos a and cos b to find the values of sin a and sin b. Thus: sin a = 3/5 and sin b = 24/25 Then substituted back into compound angle formula: cos (a+b) = (4/5)*(7/25) - (3/5)*(24/25) Simplifying gives me 28/125 - 72/125, and thus cos (a+b)= -44/125. Then I found the angle cos (a+b) using a calculator: 111° And used that to find the second possible angle: 180°-111°= 69° Then I did took cos (69°) to get the second value of cos (a+b), which according to the calculator is 0.351. But according to my textbook answers, the second value of cos (a+b) is 4/5. Can you help explain where I made a mistake, and even more is there a shorter way to solve this type of question? Thanks for you help.

3. ## Spanish B SL Revision

Yes I understand what you say about paper 1, but getting exposure to as much new vocabulary as possible should help. And in the exam you have the line numbers given to you for guidance, so even if you don't understand much of the text you should know where you can look. For paper 2 choosing two of the optional topics could work, but if you really want to maximise your potential to score high, I recommend that you study all of them (at least briefly, but you can focus on health and free time more intensely) so you can be sure to find one in the six questions that you like and write a text type you enjoy.
4. ## Spanish B SL Revision

Aside from doing past paper 1 and 2 questions and having your teacher correct them, I suggest you do the vocabulary and grammar exercises on ver-taal.com. I also use this site for practicing vocabulary and grammar and it helps me a lot. Also the site has "anuncios", "telediarios" and "traileres de películas" for you to practise understanding and applying vocabulary and grammar. If you struggle on Paper 2 it is best to practise writing a variety of text types (eg. 1 text a week, maybe a newspaper article this week, then a blog post, and then a letter) and having your teacher go over all the mistakes with you.
5. ## Help with maths question

Or for part (b) you can also start solving it algebraically: u1*rn = 40 (establish equation using the formula for geometric equations in the formula booklet) Rearrange the equation: rn = 40/u1 Substitute for u1: rn =40/(1/81) So: rn= 40*81 which is 3240 Using logarithms: log3 3240 = n On a non-calculator find out 3 to the power of what number is greater than 3240 using trial and error: eg. 35 = 243 36 = 729 37 = 2187 38 = 6561 On a calculator just use the log solver to find that n = 8
6. ## Geography IA Migration???

Dear Amrutha, It is definitely possible to do an internal assessment on migration (or another topic from Populations in Transition). It may however be that the IB does not encourage this, because of: inappropriate assignments submitted by other candidates in the years before the difficulty of collecting primary data for this topic These are the reasons I suspect, so they may be different from what your teacher finds out for you. Both of these reasons, however, do not rule out doing an internal assessment on the Populations section (though I believe that this section has been overdone, so you may want to find an interesting angle to your investigation that is unlikely to have been previously investigated). Nevertheless, you should be able to select an appropriate subtopic , explore relevant theories studied in your course (eg. Lee model of pull and push factors, Zipf's inverse distance law of migration, Earnst ravenstein Pattern of migration, and Stouffer model of intervening opportunities) and find a suitable method of investigation. BTW, what options are you studying? As you're from Brunei, you may be able to do an IA on the options: coastal margins, extreme environments, hazards and disasters, or you could do something related to urban environments, which should be possible in most places no matter the geographical limitations.
7. ## Which Geography Syllabus for 2018 November Exams?

According to my Geography teacher, the current syllabus should be valid as well for 2018, as else one should have been published by latest June 2016. But she also said that the IB may be running late this year, so to be 100% sure, I would wait till February 2017. If by then no new syllabus has been published, you should be tested on the current syllabus.
8. ## Easy Geography optional topics?

Yes my teacher says that leisure sport and tourism and urban environments are the two easiest topics
9. ## Easy Geography optional topics?

Yes, and urban environments.

11. ## Logarithms and equations question

Hey everyone, Could you please help me on the following question? Solve the following system of equations. logx+1y = 2 logy+1x = 1/4 I understand how to start ie. (x+1)2=y (y+1)=x4 Then, (x+1)2= x4-1 Can you explain the steps I need to do next to solve the equation. I found the answers, but I don't understand how anyone would procede from where I stopped. x = −1, not possible x =1.70, y = 7.27 Thanks for your help
12. ## List of Useful Websites for IB Geography SL and HL

List of Useful Websites for IB Geography SL and HL View File I've gathered the best geography resources I could find for IB students. Greenfieldgeography and The Geographer Online have materials for all the topics, while IGCSE Geography and Budding Geographers are still developing fresh content. IGCSE Geography has just released a great online course on time-space convergence. Submitter astonky Submitted 10/14/2016 Category Geography