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He seems to assume that everyone that hasn't blatantly stated they are in college or higher are in high school. I think it would be better for him if he stopped assuming that when someone says something that he doesn't agree with that it's because they are less advanced than him. Although, he probably doesn't do this on as broad a scale as I may have made it seem here, it's still an observation I've made in at least a couple examples recently. Maybe the only reason it appeared like this is because he somehow thought AntiSleep said he was in High School at some point. And, wouldn't that make high school stats even easier? I'm relatively positive that stats in high school is damn easy. ![]() ![]() ![]() ![]() ![]() ![]() ![]() |
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Depends on how you define "repetition." Repetition of a concept, not necessarily exact copies of equations where only one or two variables are changed in the structure, helps you learn. Like for instance, find the particular solution of this second order linear nonhomogeneous equation:
y"-3y'-4y = 3e^(2t) to solve this, you would use these steps: r^2-3r-4=0 r = 4 or -1 y = c_1e^(4t)+c_2e^(-t)+Y(t) Y(t) = Ae^(2t) Y'(t) = 2Ae^(2t) Y"(t) = 4Ae^(2t) Subsituting back into the original equation.. (4A-6A-4A)e^(2t) = 3e^(2t) Hence A = -1/2 thus the solution is: y = c_1e^(4t)+c_2e^(-t)-1/2e^(2t) So after solving that and not doing anymore problems like this, can you therefore say that you know how to solve second order nonhomogeneous equations? No you can't, because depending on the situation of the equation, you will need to use different steps. If you try doing exactly what we did in the previous question for this one: y"-3y'-4y = -8(e^t)cos2t they look the same, but you can't exactly use the same series of steps to solve it. Instead you use these series of steps to find the general solution: r^2-3r-4=0 r = 4 or -1 y = c_1e^(4t)+c_2e^(-t)+Y(t) Y(t) = A(e^t)cos2t+B(e^t)sin2t Y'(t) = (A+2B)(e^t)cos2t+(-2A+B)(e^t)sin2t Y"(t) = (-3A+4B)(e^t)cos2t+(-4A-3B)(e^t)sin2t substitute these into the original equation, we get: 10A+2B = 8, 2A-10B = 0 Hence A = 10/13 and B = 2/13 so therefore the answer is: y = c_1e^(4t)+c_2e^(-t)+10/13(e^t)cos2t+2/13(e^t)sin2t Both are same concept, just each using their own way of solving it. But then there can be some others that vary even more like: y''+4y = 3csct where the solution and the steps involved are: y''+4y = 0 y_c(t) = c_1cos2t+c_2sin2t y = u_1(t)cos2t+u_2(t)sin2t y' = -2u_1(t)sin2t+2u_2(t)cos2t+u'_1(t)cos2t+u'_2(t)sin2t we assume u'_1(t)cos2t+u'_2(t)sin2t = 0 so: y' = -2u_1(t)sin2t+2u_2(t)cos2t y" = -4u_1(t)cos2t-4u_2(t)sin2t-2u'_1(t)sin2t+2u'_2(t)cos2t Then substituting back into the original equation, we get: -2u'_1(t)sin2t+2u'_2(t)cos2t = 3csct now using that and our assumption: u'_1(t)cos2t+u'_2(t)sin2t = 0, we get: u'_1 = -3cost u'_2 = 3/2csct-3sint u_1 = -3sint+c_1 u_2 = 3/2ln|csct-cott|+3cost+c_2 now substituting those u's, we get: y = -3sintcos2t+3/2ln|csct-cott|sin2t+3costsin2t+c_1cos2t+c_2sin2t and using double-angle formulas, we get: y = 3sint+3/2ln|csct-cott|sin2t+c_1cos2t+c_2sin2t Again all are of which are the same concept. If you do alot more of these problems, you learn new methods of knowing how to solve them and more importantly, practical thinking and analytical skills when trying to mix, match, and apply these different methods of solving these equations. This is also a way of constant building; by learning more methods of how to solve these problems and being exposed to more and more different ways of applying methods into solving such equations helps one learn and understand the concept inside out. Repetition in this sense works. This post was edited 1 time, last edit by MillenniumArmy: Oct 8 2007, 4:38 am.
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I don't like trig. However, we've recently been introduced to radians, which makes the entire subject A LOT easier. Either way, I still don't like it, mainly because there's so much crap to memorize. It gets even worse with Vector Navigation is physics. There are no concepts. It's all stuff you already know, but need to apply it exactly, with numerous (relatively) complex equations. However, that doesn't mean I don't understand the importance. I do, and I reluctantly do 100% of my homework in it.
I like higher level questions. They're the best way to improve your understanding in a concept. ![]() ![]() ![]() ![]() ![]() ![]() |
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