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3.9 Derivatives of Exponential & Logarithmic Functions. What you’ll learn about Derivatives of e x , a x , ln x , log a x Power Rule for Arbitrary Real Powers Why?
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3.9 Derivatives of Exponential & Logarithmic Functions What you’ll learn about Derivatives of ex, ax, ln x, logax Power Rule for Arbitrary Real Powers Why? The relationship between exponential and logarithmic functions provides a powerful differentiation tool called logarithmic differentiation.
Derivatives Copy onto derivative sheet, then memorize.
Let’s use these formulas! Using find Using find
At what point on the graph of the function y=3t – 4 does the tangent line have slope 12? How can we find this out? • Find dy/dt and set it equal to zero. • Solve for t. • Evaluate f(t) in the original equation. • Hint: t is a messy number, store value for accuracy in final answer.
A line with slope m=1/a passes through the origin and is tangent to the graph of y = ln x. What is the value of m? We know • Point of tangency has coordinates (a, ln a) for some positive a • Tangent line has slope m = 1/a • Tangent line passes through the origin so equation has point (0, 0) Find slope with formula and set it equal to 1/a. Solve for a.
Homework Page 178 Quick Review 1-10 Exercise 3-21 (3n, nЄI)
Going the long way with the chain rule! Find a = u(x)= u’(x) =
You try a = u = u’ =
Using the power rule in all of its Power! Find each derivative using
What does it mean to “Find Domain”? If f(x) = ln (x - 6), find f ’(x). State the domain of f ’. • Find f ’ • Where is f ’ defined?
Sometimes we should use logarithms to simplify before differentiation. Find dy/dx for y = x x • Use logs to lose the exponent, THEN take the derivative implicitly.
How Fast does H1N1 Spread? The spread of a flu in a certain school is modeled by the equation Where P(t) is the total number of students infected t days after the flu was first noticed. Many of them may already be well again at time t. • Estimate the initial number of students infected with the flu. • How fast is the flu spreading after 3 days? • When will the flu spread at its maximum rate? What is this rate?
Homework Page 178 Exercises 24-39 (3n, nЄI), 53, 56-62 & Study for Quiz: 3.7 thru 3.9