Gilbert Strang; Edwin “Jed” Herman

Review Exercises

True or False? Justify the answer with a proof or a counterexample.

367.

Every function has a derivative.

368.

A continuous function has a continuous derivative.

369.

A continuous function has a derivative.

370.

If a function is differentiable, it is continuous.

Use the limit definition of the derivative to exactly evaluate the derivative.

371.

$f (x) = \sqrt{x + 4}$

372.

$f (x) = \frac{3}{x}$

Find the derivatives of the following functions.

373.

$f (x) = 3 x^{3} - \frac{4}{x^{2}}$

374.

$f (x) = {(4 - x^{2})}^{3}$

375.

$f (x) = e^{sin x}$

376.

$f (x) = ln (x + 2)$

377.

$f (x) = x^{2} cos x + x tan (x)$

378.

$f (x) = \sqrt{3 x^{2} + 2}$

379.

$f (x) = \frac{x}{4} {sin}^{−1} (x)$

380.

$x^{2} y = (y + 2) + x y sin (x)$

Find the following derivatives of various orders.

381.

First derivative of $y = x ln (x) cos x$

382.

Third derivative of $y = {(3 x + 2)}^{2}$

383.

Second derivative of $y = 4^{x} + x^{2} sin (x)$

Find the equation of the tangent line to the following equations at the specified point.

384.

$y = {cos}^{−1} (x) + x$ at $x = 0$

385.

$y = x + e^{x} - \frac{1}{x}$ at $x = 1$

Draw the derivative for the following graphs.

386.

The function begins at (−3, 0.5) and decreases to a local minimum at (−2.3, −2). Then the function increases through (−1.5, 0) and slows its increase through (0, 2). It then slowly increases to a local maximum at (2.3, 6) before decreasing to (3, 3).

387.

The function decreases linearly from (−1, 4) to the origin, at which point it increases as x2, passing through (1, 1) and (2, 4).

The following questions concern the water level in Ocean City, New Jersey, in January, which can be approximated by $w (t) = 1.9 + 2.9 cos (\frac{π}{6} t),$ where t is measured in hours after midnight, and the height is measured in feet.

388.

Find and graph the derivative. What is the physical meaning?

389.

Find $w^{'} (3) .$ What is the physical meaning of this value?

The following questions consider the wind speeds of Hurricane Katrina, which affected New Orleans, Louisiana, in August 2005. The data are displayed in a table.

Hours after Midnight, August 26	Wind Speed (mph)
1	45
5	75
11	100
29	115
49	145
58	175
73	155
81	125
85	95
107	35

Table 3.9 Wind Speeds of Hurricane Katrina Source: http://news.nationalgeographic.com/news/2005/09/0914_050914_katrina_timeline.html.

390.

Using the table, estimate the derivative of the wind speed at hour 39. What is the physical meaning?

391.

Estimate the derivative of the wind speed at hour 83. What is the physical meaning?