Jamie's Bird Got Poisoned

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Jamie's Bird Got Poisoned

  1. 1. Differential Equations: Poisoned Bird Questions Mushroom Eater by Flickr user: Just Emi
  2. 2. a) Oh no! Jamie’s pet duck ate the poisonous mushroom! Luckily, Bench knows what type of mushroom it is. The Fungus Differentius has a very dangerous toxin. When eaten, it can cause mutations. (Don’t you think the duck has had enough torture?) The rate at which the poison is spreading throughout the duck is defined as dp/dt. Sketch a slope field for at the points indicated.
  3. 3. b) Use Euler’s Method to approximate the solution of dp/dt with the initial condition of with 5 steps of size 0.2. c) Find a particular solution to dp/dt with the initial condition .
  4. 4. Differential Equations: Mushroom Scene
  5. 5.  Ifwe take a coordinate that’s given on the graph and plug the coordinate’s x- and y-values into the differential equation, we obtain the slope at that point
  6. 6.  Example:
  7. 7.  Bycreating a display of lines (the slope field), where each line indicates the slope at that point, we can see the parent function  That is, the solution of a derivative via slope fields is the parent function
  8. 8.  Therefore, by shortening the distance between the points, a smoother line is generated, making the function we’ve created further resemble the parent function  Allow ∆x to be infinitesimally small, we have the parent function!
  9. 9.  Thevalues on the grid below correspond to the position of the coordinates on the graph:  The value in cell A1 represents the coordinates (-4, 4) on the graph
  10. 10. Differential Equations: Mushroom Scene
  11. 11.  Using Euler’s Method, we start at the initial coordinates,  In this case, at (3, 3.0642)  Note that all values in the graphs above are rounded to four decimal places for simplicity
  12. 12.  By plugging the P0 coordinates into the differential equation, y’, we obtain y’ at P0  In this case, we plugged (3, 3.0642) into to obtain dp/dt = 29.4975
  13. 13.  We know the definition of a slope as the rise (the change in the dependent variable) over the run (the change in the independent variable)  By multiplying y’ (the slope) by ∆x (the run), we obtain ∆y (the rise)
  14. 14.  We’re given that ∆x = 0.2  Adding ∆y to y0, we obtain y1  We repeat this process until we reach the number of desired steps
  15. 15.  Note that all values in the table above are given in their decimal form, rounded to four decimal places for simplicity
  16. 16. Differential Equations: Mushroom Scene
  17. 17.  We can separate the variables, that is, in this case, antidifferentiating t on one side with respect to dt and p on one side with respect to dp  Separatingthe variables is analogous to antidifferentiating after solving for ∆y when given the definition of a slope
  18. 18.  Integration by parts is an antidifferentiation technique we can use when we have to antidifferentiate two factors  We’re undoing the product rule Formula for integration by parts:
  19. 19. LIATE is a mnemonic used to determine which of the factors should be selected for f. LIATE tells us the order of preference for f. L I A T E O N L R X G V G I E P A E G O R R B O S N I E R N T A M E H T I E N M R C T T I I R I C G I O A N C L O M E T R I C
  20. 20.  Bench says: I have discovered a rule for differentiating products involving et without using the whole process of integration by parts or LIATE! MWAHAHA!
  21. 21.  Thepower rule says that the derivative of any variable to an exponent can be found by multiplying the term by the exponent and decrease the exponent by 1
  22. 22. • Differentiate the algebraic factor until we get a constant • Note that the signs alternate: minus, plus, minus, plus, et c. • In this case: t2 – 2t + 2
  23. 23.  We’re given the initial value  We can use this fact to determine C * Remember, C is a constant! Note:  Since we’re antidifferentiating, we’d expect C’s on both sides  Let’s group the C’s to one side of the equation for simplicity
  24. 24.  Puttingit all together, we now have a general solution for p
  25. 25. Bench: Now that I know how the poison reacts in the bird, I can cure it. Jamie: Hurry up! Save my bird!
  26. 26. Was I a Cockatoo at the beginning? I think the bird is happy and healthy now… Happy Bird 1 by Flickr user: Calsidyrose

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