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Learn how to maximize the area of a rectangular pen with limited fencing using absolute extrema concepts. Experiment, study, and solve exercises to master the strategies for finding absolute maxima and minima.
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Absolute Extrema Lesson 6.1
Fencing the Maximum • You have 500 feet of fencing to build a rectangular pen. • What are the dimensions which give you the most area of the pen • Experimentwith Excelspreadsheet
Intuitive Definition • Absolute max or min is the largest/smallest possible value of the function • Absolute extrema often coincide with relative extrema • A function mayhave several relative extrema • It never has more than one absolute max or min
Reminder – the absolute max or min is a y-value, not an x-value Formal Definition • Given f(x) defined on interval • The number c belongs to the interval • Then f(c) is the absolute minimum of f on the interval if • … for all x in the interval • Similarly f(c) is the absolute maximum if for all x in the interval c f(c)
Functions on Closed Interval • Extreme Value Theorem • A function f on continuous close interval [a, b] will have both an absolute max and min on the interval • Find all absolute maximums, minimums
Strategy • To find absolute extrema for f on [a, b] • Find all critical numbers for f in open interval (a, b) • Evaluate f for the critical numbers in (a, b) • Evaluate f(a), f(b) from [a, b] • Largest value from step 2 or 3 is absolute max • Smallest value is absolute min
Try It Out • For the functions and intervals given, determine the absolute max and min
Graphical Optimization • Consider a graph that shows production output as a function of hours of labor used We seek the hours of labor to use to maximize output per hour of labor. Output hours of labor
Note that this is also the slope of the line from the origin through a given point Graphical Optimization • For any point on the curve • x-coordinate measures hours of labor • y-coordinate measures output • Thus We seek to maximize this value Output hours of labor
Graphical Optimization • It can be shown that what we seek is the solution to the equation Now we have the (x, y) where the line through the origin and tangent to the curve is the steepest Output hours of labor
Assignment • Lesson 6.1 • Page 372 • Exercises 1 – 53 odd