Tabbris Posted February 21, 2010 Report Share Posted February 21, 2010 Hi there!I just wanted to say (just in case anyone finds it useful) that I created a very precise equation using the sine function and transformations. It was something like:y=a(sin(b(x-h))+kHope YOu find it useful!!! Reply Link to post Share on other sites More sharing options...
sweetnsimple786 Posted February 21, 2010 Report Share Posted February 21, 2010 Sine wave does fit it well, but my friend got really low marks for her math part because she used sine for BMI because it didn't make sense. Like you wouldn't expect the BMI to go up and down in a cyclical fashion, so my teacher took off points. Maybe it wasn't deserved? I don't know. I just wanted to put that warning out there. You can always ask your teacher. [if he/she responds or not is another matter...] Reply Link to post Share on other sites More sharing options...
123456789 Posted February 24, 2010 Report Share Posted February 24, 2010 no Reply Link to post Share on other sites More sharing options...
Austin Glau Posted February 24, 2010 Report Share Posted February 24, 2010 What do you mean "no"? Reply Link to post Share on other sites More sharing options...
xoxohkd Posted February 27, 2010 Report Share Posted February 27, 2010 Hey I have just got started on the math portfolio and i am really not sure about how to go about doing it.the question asks to define variable but what are the variables? and what does it mean my function models?someone please come to my rescuee Reply Link to post Share on other sites More sharing options...
masochist Posted February 27, 2010 Report Share Posted February 27, 2010 Variables are x and y - the varying unknowns that you plug in.For example in the linear function: y=mx+b, the variables are x and y. Reply Link to post Share on other sites More sharing options...
xoxohkd Posted February 27, 2010 Report Share Posted February 27, 2010 thankshey we have the same subject combinations and i am doing geog for ee too.but im still unsure of how to do the portfolio Reply Link to post Share on other sites More sharing options...
Charizard Posted February 28, 2010 Report Share Posted February 28, 2010 Hey I have just got started on the math portfolio and i am really not sure about how to go about doing it.the question asks to define variable but what are the variables? and what does it mean my function models?someone please come to my rescuee 'function model': Well my IA sheet says 'model function' but basically the task of the assignment is to 'model' a function that fits the data; that is, to find a function (eg linear, quadratic, logarithmic) that fits the data well and shows you the right trend. So your model function / function model should be the function you're using.Also, yes the variables are the things you change, usually the x and y in the functions that you learn. Remember to rename them to fit your data well - my teacher keeps stressing this even though it would technically be okay to use x and y as long as you defined them. One common example would be H for height and t for time. So for yours you could use something like A for the BMI of American females and Z for the BMI of Zimbabwean females etc. Reply Link to post Share on other sites More sharing options...
123456789 Posted March 6, 2010 Report Share Posted March 6, 2010 easy stuff though...Dont worry about it. Reply Link to post Share on other sites More sharing options...
pomoni Posted March 13, 2010 Report Share Posted March 13, 2010 Hi guys!My friend and I are a bit confused about finding a model that fits the points... do they want us to find them only by calculations, or can we use programs like the autograph? Please help!!! & thanks. Reply Link to post Share on other sites More sharing options...
bLub Posted March 13, 2010 Report Share Posted March 13, 2010 well I did sine, then a cubic function and finally a quartic function which fitted best - and got 19! Reply Link to post Share on other sites More sharing options...
pomoni Posted March 13, 2010 Report Share Posted March 13, 2010 Yeah but my question is, did you find it manually, or using some program? Did you use some formula to get the coefficients? Or did you just use a program? Reply Link to post Share on other sites More sharing options...
sweetnsimple786 Posted March 13, 2010 Report Share Posted March 13, 2010 You need to first find it manually [analytically] and then you need to use a program/graphing calculator. Reply Link to post Share on other sites More sharing options...
pomoni Posted March 13, 2010 Report Share Posted March 13, 2010 The thing is I heard people solving previous Math IAs using the calculator (when they weren't really supposed to) and they still got a full grade on the IA. And our teacher also told us we can use the autograph program, so I'm pretty confused about this. I don't even know how to get the solution manually only when I'm using a quadratic function... Reply Link to post Share on other sites More sharing options...
sweetnsimple786 Posted March 13, 2010 Report Share Posted March 13, 2010 As long as you show the work for the manual part, you're fine. You can use a calculator, figure out what you need as the model, and then go about solving it. For manual.. you're using a quadratic function? Like a parabola? If it looks like a parabola will fit the data points, then what you do is get a general equation. y=ax2 +bx +cThen you find a, b, and c. Do you know how to do this using a system of equations? Reply Link to post Share on other sites More sharing options...
pomoni Posted March 13, 2010 Report Share Posted March 13, 2010 I'm using "y=ax^4+bx^3+cx^2+dx+e" for my model. I am however not really familiar with solving this using a system of equations. I would be grateful if you told me how it is applicable in this situation. Reply Link to post Share on other sites More sharing options...
sweetnsimple786 Posted March 13, 2010 Report Share Posted March 13, 2010 Okay, you're using a quartic [quadratic = 2 as highest power of x & quartic = 4 as highest power]You use points from the data. The points are in the form (x, y). When you plug these points into your general formula, you'll get a system of equations. You want to use n points if you have n unknowns. So if you have 5 unknowns, you want to use 5 points. You can google it to get more details for the actual solving part. I love PurpleMath. =) Reply Link to post Share on other sites More sharing options...
pomoni Posted March 13, 2010 Report Share Posted March 13, 2010 Okay, I'll try my luck with these.. and sorry about calling it a quadratic hahaha I hate math and I'm really bad at everything related to it. Thanks a lot Reply Link to post Share on other sites More sharing options...
eemma Posted March 14, 2010 Report Share Posted March 14, 2010 Okay, so my equation for number 2 is a sine function. I used cubic and quartic for number three, where I used a calculator. My problem is showing the work/calculations for how I derived the sine function. I sort of just plugged in random values and guessed and checked...pretty sure that's not what IB is looking for. How do I show my manual calculations for the sine function that I used to fit the raw data? Reply Link to post Share on other sites More sharing options...
sweetnsimple786 Posted March 14, 2010 Report Share Posted March 14, 2010 What does your general formula look like? y=Asinx + B? You're probably going to want something more complicated than that. What we've discussed above is that for each unknown [A, B, etc], you need an equation to make a system of equations to solve for the unknowns. You do this by plugging in points from the data you're give. PurpleMath Reply Link to post Share on other sites More sharing options...
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