150 likes | 209 Views
Photo by Vickie Kelly, 2003. 3.2 Differentiability. Arches National Park. Created by Greg Kelly, Hanford High School, Richland, Washington Revised by Terry Luskin, Dover-Sherborn HS, Dover, Massachusetts. Photo by Vickie Kelly, 2003. Greg Kelly, Hanford High School, Richland, Washington.
E N D
Photo by Vickie Kelly, 2003 3.2 Differentiability Arches National Park Created by Greg Kelly, Hanford High School, Richland, Washington Revised by Terry Luskin, Dover-Sherborn HS, Dover, Massachusetts
Photo by Vickie Kelly, 2003 Greg Kelly, Hanford High School, Richland, Washington Arches National Park
What function is this? Does the window setting matter?
For a function like y = x^5 – 6x… Zooming in makes the curve straighten out… “Differentiable functions are continuous and locally linear” (but not vertical!)…
A derivative will fail to existat any x-value where the slope of f(x) changes drastically or is undefined, or at an x-value where f(x) is discontinuous: corner at x = 0 cusp at x = 0 discontinuity at x = 0 vertical tangent at x = 0
Most of the functions we study in calculus will be differentiable!
Derivatives on the TI-83/84: You must be able to calculate derivatives with the calculator and without (using limits) .
nDeriv( x ^ 3, x, 2) ENTER Find at x = 2 Example: From your home screen, the MATH 8 command calculates the derivative of y1 “at” a point; the syntax is: nDeriv(function, independent variable, coordinate) 12 From your y= screen, the MATH 8 command calculates and plots the derivative of function y1at all xvalues in the window: the SLOPES along y1 are graphed as the HEIGHTS on y2 y1 = x^3 y2 = nDeriv(y1, x, x)
W a r n I n g: The calculator can return an incorrect value if you try to evaluate a derivative at a point where the function is not differentiable (at a discontinuity, a cusp, a corner, or a vertical tangent location!). This is known as “grapher failure.” Examples: nDeriv(1/x,x,0) returns 1,000,000 (or some other large number!) nDeriv(abs(x),x,0) returns 0
Graphing Derivatives You may recognize the patterns of some derivative graphs! Graph: Y1=nDeriv(lnx, x, x) This graph looks like:
Iff has a derivative at x = a, thenf is continuous at x = a. There are two theorems on page 110: (Since a function must be continuous to have a derivative: limit = f(a) = limit x →a- x→a+ then each function that has a derivative is already continuous on its domain.) A typical logic error by beginning calculus students is to try to switch the “if” and the “then”, thereby creating the converse (which may or MAY NOT be true!!!)
If a and b are any two x-values in an interval on which f is differentiable, then takes on every value between and . Intermediate Value Theorem for Derivatives The slope takes on every value between the slope at aand the slope at b …for this function, every slope between ½ and 3. p