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  1. Totalderiv

    Complex Eigenvalues

    Homework Statement Apply the eigenvalue method to find a general solution of the given system. x_1' = 5x_1 - 9x_2 x_2' = 2x_1 - x_2 Homework Equations (A-λI)v=0 The Attempt at a Solution x_1' = 5x_1 - 9x_2 x_2' = 2x_1 - x_2 \left[ \begin{array}{cc} 5-λ & -9\\ 2 & -1-λ...
  2. Totalderiv

    Matrices and Linear Systems

    Homework Statement Write the given system in the form x'=P(t)x + f(t) x'=-3y , y'=3x Homework Equations x'=P(t)x + f(t) x(t)=c_1x_1(t)+c_2x_2(t)+...+c_nx_n(t) The Attempt at a Solution I have no idea how to start this since my teacher never covered this in our notes and the book...
  3. Totalderiv

    Find a general solution of the differential equation

    So it would be; y=zx y'= z+xz' z+xz' =\frac {1-z}{1+z} How do I isolate the z's and x's in order to integrate?
  4. Totalderiv

    Find a general solution of the differential equation

    Homework Statement Find a general solution of the differential equation. (x+y)y' = x-y Homework Equations v=x+y y=v-x y'=v'-1 The Attempt at a Solution So if I plug this back into the original equation; v(v'-1)= x-y How do I convert v=x+y into x-y so that I have only v's...
  5. Totalderiv

    Am I really cut for math?

    This has been said many times on this forum, but math is extremely interesting when you move past Calculus. However, math becomes extremely difficult to understand if you don't train yourself to get out of the "computational" mode that high school and basic college math courses teach you. Once...
  6. Totalderiv

    Complex integration

    Try using the identity: \int \frac {du}{a^2 + u^2} = \frac{1}{a}arctan\frac{u}{a} +c
  7. Totalderiv

    Diff Eq- Nonhomogeneous Equations

    Homework Statement Find a particular solution of the given equation. y^''' + 4y^' = 3x-1 Homework Equations r^3 + 4r = 0 r = 0, r = 2i, r = -2i The Attempt at a Solution y(x) = Ax-B y^'(x) = A y^''(x) = 0 y^'''(x) = 0 The answer is: y(x)=(3/8)x^2 - (1/4)x But I'm not...
  8. Totalderiv

    Programs Physics degree, need advice.

    The only way you could prove that you have the knowledge is to test out of the course via CLEP, AP, or DSST. But, these are only limited to high school and basic college courses. Colleges won't let you test out of a higher-level course because you proclaim that you self-studied it.
  9. Totalderiv

    Programs Physics degree, need advice.

    With this logic you're going to be living just above the poverty line in any of those countries. You must account for the cost of living standards, goods, and services when you move to another country. Self-study isn't worth anything to an university or a college if you can't prove that you...
  10. Totalderiv

    Dot and Cross Products

    The vector of \left|u \times v\right| = \left|\begin{array}{cc}i & j & k\\u_1 & u_2 & u_3\\v_1 & v_2 &v_3\end{array}\right|Then substitute in u for i,j,k because you're trying to prove that the vector \left|u \times v\right| is orthogonal to both u and v. Then simplify and distribute.
  11. Totalderiv

    Programs I think I want to be a math major?

    Before you start studying Calculus you may want to brush up on Algebra, Geometry, and Trigonometry because your knowledge in these classes will be important when you take Calculus. Not to be harsh, but if you got a B- in Algebra then you may want to rethink this decision because you're far from...
  12. Totalderiv

    Why does Lim as x approaches infinity of x/(x-9) = 1?

    A nice trick for these types of problems would be to divide everything by x; \lim_{x\rightarrow\infty} \frac{x/x}{(x/x)-(9/x)} Then simplify and you should be able to figure it out from there
  13. Totalderiv

    Testing Exam nerves!

    Did you feel like you were rushing through the exam? Try to slow down when reading the questions and prepare yourself with sample questions the night before. In my math classes it seems like I'm the only one who is not anxious or nervous at all on the day of mid-terms/finals, try to relax...
  14. Totalderiv

    Not sure what career in technology I want.

    Since you still have another year of high school left, take another math course and physics course since you're interested in Engineering. Usually the university that you go to will have you take the basic prerequisites for all Engineering majors for the first year. So you can easily change your...
  15. Totalderiv

    Does it get better after school?

    If you like Engineering and you want to get your hands dirty, then you should look into civil engineering or electrical engineering. The concepts that you learn in college will help you once you are out in the work force.
  16. Totalderiv

    A good Prerequisite

    You shouldn't be worrying about getting a PhD when you just started high school! When I was your age I thought that I would get a PhD in Mathematics and work in the Finance Industry. But now I'm a freshman in college and changing my major from Mathematics to Civil Engineering because I caught a...
  17. Totalderiv

    Programs Pure math PhD going into the industry. What are the chances?

    I'm a freshman math major and just finished my first semester. This thread has me very worried about my future.
  18. Totalderiv

    Programs Do you need a PhD to become a quant?

    Most quant jobs require a PhD, so I would say yes.
  19. Totalderiv

    Is THIS really the correct way to judge math and science talent ?

    The kids who do well on the Olympiad exams/SAT test(primarily Math section) obviously have some talent because they are able to comprehend what is being asked of them...and that's half the battle with these tests.
  20. Totalderiv

    Advice on learning Calculus II on my own.

    Get a textbook and do a lot of practice problems. I just finished up Calc II and it isn't a cake-walk even with a professor. Kudos to you if you're able to pull it off!
  21. Totalderiv

    Post your spring schedule!

    Calculus III Intro to Differential Equations Intro to Linear Algebra World Civ 2 Advanced Writing 1
  22. Totalderiv

    Programs Spring Classes (Freshman Math Major): Too much?

    The description says "Linear equations, matrices, determinants, vector spaces, linear mappings, inner products, eigenvalues, eigenvectors." Right now I'm expecting an A in my Calc 2 class.
  23. Totalderiv

    Programs Spring Classes (Freshman Math Major): Too much?

    Hey I'm currently a freshman math major and just registered for my spring classes. When I went to my adviser, she thought I was insane for taking three math classes at one time. Am I insane? Schedule: -College Calculus 3 -Introduction to Differential Equations -Introduction to Linear...
  24. Totalderiv

    Solving Trig Integrals help!

    I could either do \int cos^3(x) * cos^3(x) or \int (cos^2(x))^2 * cos^2(x) or \int cos^4(x) * cos^2(x) I have tried all of these, but couldn't get an answer unless I'm supposed to use the half-angle identities. Any one have a clue on how I should split this up?
  25. Totalderiv

    Solving Trig Integrals help!

    Homework Statement \int cos^6(x) Homework Equations 1 = sin^2(x) + cos^2(x) The Attempt at a Solution \int cos(x) * cos^5(x) \int cos(x) * (cos^2(x))^3 \int cos(x) * (1-sin^2(x))^3 This is where I got lost, we just started this topic and I have a lot of homework to do...
  26. Totalderiv

    Summer getting too hard for you? Post your Fall Schedule to cool down!

    Freshman fall schedule(going for Math major with classes in computer science): -Intro to CS majors -Writing 1 -Calc II -University Seminar -World Civ What do you guys think?
  27. Totalderiv

    Programs New Math Major scheduling help!

    Hey I'm currently headed off to University at Buffalo this fall for math and I'm stuck on scheduling. So far I know I'm talking Calculus II, but I'm not sure what else to take. What classes should I take as a freshman math major?
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