## Practice Problems

Work through the odd-numbered problems 1-21. Once you have completed the problem set, check your answers.

### Answers

(b) Hypotenuse so so is increasing.

(c) Perimeter so so is increasing.

9. for all so and so and When and , then .

11. Let be the distance from the lamp post to the person, and be the length of the shadow, both in feet. By similar triangles, so .

(The value of does not enter into the calculations).

(b) length of the string so and .

(3 . The volume is increasing at about .

17. Given: with constant. We also have so .

Therefore, so . The radius is changing at a constant rate.

For parts (b) and (c) we need to work in radians since our formulas for the derivatives of the trigonometric functions assume that the angles are measured in radians: radians so radians and radians,

(The " - " indicates the distance to the sign is decreasing: you are approaching the sign). Your speed is .