Finite notes – 8.5 Higher Order Derivatives The second derivative, or second order derivative, is the derivative of the derivative of a function. The derivative of the function f(x) may be denoted by , and its double (or "second") derivative is denoted by . This is read as "f double prime of x," or "The second derivative of f(x)." Because the derivative of function f is defined as a function representing the slope of function f, the double derivative is the function representing the slope of the first derivative function. Furthermore, the third derivative is the derivative of the derivative of the derivative of a function, which can be represented by . This is read as "f triple prime of x", or "The third derivative of f(x)". This can continue as long as the resulting derivative is itself differentiable, with the fourth derivative, the fifth derivative, and so on. Any derivative beyond the first derivative can be referred to as a higher order derivative. Let f(x) be a function in terms of x. The following are notations for higher order derivatives. 2nd Derivative 3rd Derivative 4th Derivative nth Derivative Notes f(4)(x) f(n)(x) Probably the most common notation. Leibniz notation. Another form of Leibniz notation. D2f D3f D4f Dnf Euler's notation. Warning: You should not write fn(x) to indicate the nth derivative, as this is easily confused with the quantity f(x) all raised to the nth power. The Leibniz notation, which is useful because of its precision, follows from . Newton's dot notation extends to the second derivative, , but typically no further in the applications where this notation is common. Finite Math – Section 8.5 - page 2 Example 1: Find the third derivative of respect to x. with Repeatedly apply the Power Rule to find the derivatives. Example: Find f ''' ( x ) and f ''' (2) of f(x)= x-2 . 4x Distance, Velocity, and Acceleration If a function, s(t), represents distance at time t, then s’(t), the 1st derivative, represents the velocity, and s’’(t), the 2nd derivative of s(t), represents acceleration. The 3rd derivative, s’’’(t) represents jerk. Remember to connect derivatives with “rate of change” of a quantity. Finite – Section 8.5 page 3 EXAMPLE Each of the following three “stories,” labeled a, b, and c, matches one of the velocity graphs, labeled (i), (ii), and (iii). For each story, choose the most appropriate graph. a. I left my home and drove to meet a friend, but I got stopped for a speeding ticket. Afterward I drove on more slowly. _______ b. I started driving but then stopped to look at the map. Realizing that I was going the wrong way, I drove back the other way. _______ c. After driving for a while I got into some stop-and-go driving. Once past the tie-up I could speed up again. _______ EXAMPLE A rocket can rise to a height of h(t ) t 3 0.5t 2 feet in t seconds. Find its velocity and acceleration 10 seconds after it is launched. Four interpretations for the derivative: 1. instantaneous rate of change 2. slope of tangent 3. marginals 4. velocity