Recent content by jrjack

  1. J

    Differentiate: r=r cos(theta)i+r sin(theta)j

    A few Multiple function product rule refresher videos later... I believe the 1st term should go from: -r \frac{d\theta}{dt} \sin(\theta) to: - \left( \frac{dr}{dt} \frac{d\theta}{dt} \sin(\theta) + r \frac{d}{dt}(\frac{d\theta}{dt} \sin (\theta)) \right) - \left( \frac{dr}{dt}...
  2. J

    Differentiate: r=r cos(theta)i+r sin(theta)j

    Ah yes, it's been 5 years since I typed anything in LaTeX either, but I wrote it correctly on my paper. Now I need a refresher on getting the second derivative of the equation. I have: \vec{r} = r \cos(\theta) \hat{i} + r \sin(\theta) \hat{j} \vec{v} = \left( -r \dot{\theta} \sin(\theta) +...
  3. J

    Differentiate: r=r cos(theta)i+r sin(theta)j

    Ok, so I don't need to chain rule the 1st cosine factor, and adding the chain rule on the cosine factor on the left: \cos(\theta) \cdot \frac{d\theta}{dt} gives: \frac{dx}{dt} = \frac d {dt}\left(r\cos(\theta)) \right) = \frac {dr}{dt} \cos(\theta) + r \cdot \left(\cos(\theta) \cdot...
  4. J

    Differentiate: r=r cos(theta)i+r sin(theta)j

    I get that r is the magnitude of \vec{r} Both r and \theta are functions of time. Let me start with only the x-side of the equation: x = r \cos (\theta) Applying the product rule to r and \cos(\theta) yields: \dot{x} = r (-\sin)(\theta) + \dot{r} \cos (\theta) And adding the...
  5. J

    Differentiate: r=r cos(theta)i+r sin(theta)j

    Homework Statement This is a problem from Dynamics but I'm mostly having trouble with the calculus. Derive an expression for the position, velocity, and acceleration of a machine in terms of: r, \dot {r}, θ, \dot{θ}, \ddot{r}, \ddot{θ}, . r = length of the arm θ = angle of the arm to the...
  6. J

    Mechanical Engineering degree/transfer student Q's, advice highly recommended.

    So, i assume math 111 is College Algebra/ Pre-Calc, and 112 is Trig. There are usually several General-Education classes that have to be taken as well as ME specific classes, you can always take those while you complete the math sequence. I do not know your specific course requirements (or...
  7. J

    Mechanical Engineering degree/transfer student Q's, advice highly recommended.

    Well, from a quick google search I think Math 65: Developmental elementary algebra, and Math 95: Developmental Intermediate Algebra, but I'm not sure if your school allows you to take Calculus 1 after that. I do not know if you can finish a ME degree before your GI bill runs out, but it does...
  8. J

    Can I Become An Engineer With a Family?

    I am 32 and married to my wife for almost 3 years and we are expecting twin boys due in October. I have been attending CC for 2 years part time getting my gen-ed requirements, and the first 2 years toward a mechanical engineering degree, out of the way. And I may be here another 2 years before...
  9. J

    Post Your Summer/Fall 2012 Class Schedules

    Summer: Work full time, Gen Ed......Macroeconomics Fall: Continue working full time, Linear Algebra Calc-based Physics 1 (online, including lab) Become Daddy of twin boys!
  10. J

    Programs Majoring in Engineering what is the sacrifice like?

    I understand your frustrations, and yes this does seem like a big sacrifice. I, too, hope it will be worth it in the end. I currently work 45hrs per week and attend community college part time (10hrs of online and night classes). I finally have most of my gen-ed classes out of the way, but...
  11. J

    Find the inverse of the polynomial.

    I am still a little confused, but thank you very much for your help. I need to find and practice another one of these.
  12. J

    Find the inverse of the polynomial.

    In this formula?(f^{-1})(a)=\frac{1}{f'((f^{-1})(a))} (f^{-1})(a)=\frac{1}{f'(1)} then f'(1)=\frac{1}{2}(25)^{-\frac{1}{2}}(6) equals 3/5, and the inverse is 5/3. So, is this the way I should go about these kind of problems?
  13. J

    Find the inverse of the polynomial.

    My choices were 2/3, 5/3, 4/3, or 7/3. I guessed 2/3, but was wrong and the correct answer was 5/3. My guessing needs work.
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