Sunday, May 2, 2010

Post #37

5 days left :) Yay Yay Yay. But i'm still calculus illiterate.

Limits:

If the bottom is 0 don’t assume the limit does not exist right away, first factor and cancel or use your calculator.

Related Rates:

1. Identify all variables and equations.
2. Identify what you are looking for.
3. Make a sketch and label.
4. Write an equations involving your variables.
*You can only have one unknown so a secondary equation may be given
5. Take the derivative with respect to time.
6. Substitute in derivative and solve.

For example, The variables x and y are differentiable functions of t and are related by the equation y = 2x^3 - x + 4. When x = 2, dx/dt = -1. Find dy/dt when x = 2.Since everything is given you can skip straight to the derivative.dy/dt=6x^2dx/dt - dx/dtNow plug in all your givens in order to find dy/dt.dy/dt=6(2)^2(-1) - (-1)dy/dt= -23

Volume by disks:
The formula is pi S[r(x)]^2dx

Volume by washers is the same as volume by disks except it has a hole in it. That means it is bounded by two graphs. The formula for volume by washers is Pi S top^2 - bottom^2 dx.

Umm my ap score seems to be dropping every single test, so I need help.

Mainly with ln and e integration and derivatives, related rates, substitution integration, remembering all the area/volume formulas, and stuff I need to figure out on my own. Even when I know what to do and know the way I have to do it I have a lot of trouble applying it and never get the answer. SO HELP.

3 comments:

  1. e integration is really easy
    the exponent e is raised to is always u
    then you take your du from u
    then the integral would be S e^u du

    ReplyDelete
  2. substitution:
    1. Find u and du
    2. set u equal to whatever isn't the derivative
    3. take the derivative of u
    4. substitute back in

    ReplyDelete
  3. Remember for e integration, your u will always be what e is raised to. So if you have a function like the integral of e^2x, your u would be 2x and your du would be 2. Hope this helps!

    ReplyDelete