Math 107.04 Exam 3 Practice: Equations, Functions, Trig, Circles, Exams of Pre-Calculus

Practice problems for exam 3 in math 107.04, focusing on solving equations, function modeling, trigonometry, and circles. Topics include using the quadratic formula to solve equations, constructing functions for bacterial population growth, evaluating trigonometric functions, finding the radius and area of a circular sector, and proving pythagorean identities.

Typology: Exams

Pre 2010

Uploaded on 08/31/2009

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Math 107.04 Exam 3 Practice Spring 2009
1. Solve the following equations for x.
(a) 73x= 4x1(b) 19
23x
4= 3 (c) 2 + 3e2x
e4x= 0
(d) ex
12ex
1 = 0 (e) log2(x+ 1) + log2(x2) = log2(3x)
(f) log9(x5) + log9(x+ 3) = 1 (g) 2 log x= log(2x)log(3x1)
pf3
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Math 107.04 Exam 3 Practice Spring 2009

  1. Solve the following equations for x.

(a) 73 x^ = 4x−^1 (b) 19 23 x^ − 4

= 3 (c) 2 + 3e^2 x^ − e^4 x^ = 0

(d) ex^ − 12 e−x^ − 1 = 0 (e) log 2 (x + 1) + log 2 (x − 2) = log 2 (3x)

(f) log 9 (x − 5) + log 9 (x + 3) = 1 (g) 2 log x = log(2x) − log(3x − 1)

  1. A certain type of bacteria dies when exposed to light. If a population of 20, 000 of these bacteria are exposed to light for 15 seconds, their population declines to 2, 000. Assume that the population of bacteria follows the model:

n(t) = n 0 ekt

where t is measured in seconds.

(a) Construct a function that models the bacteria population after t seconds of light exposure.

(b) How long must the population be exposed to light to decline to 2 bacteria?.

  1. Another type of bacteria thrives when immersed in water. If a population of 30, 000 of these bacteria are immersed for 30 seconds, their population grows to 120, 000. Assume that the population of bacteria follows the model:

n(t) = n 0 ekt

where t is measured in seconds.

(a) Construct a function that models the bacteria population after t seconds of immersion.

(b) How long must the population be immersed to grow to 240, 000 bacteria?.

  1. An arc of length 4 ft on the circle subtends a central angle of 225◦.

(a) Find the radius of the circle. (b) Find the area of the circular sector.

  1. (a) Sketch a (right) triangle that has acute angle θ if csc θ = 1611 , and find the other five trigonometric ratios of θ.

(b) If θ in part (a) is in quadrant IV rather than quadrant I, which of the six trigonometric ratios found in (a) must change sign? Justify your answer.

  1. A man 6-ft tall is standing 10 ft from a lamppost. If the angle of depression from the lamppost to the tip of his shadow is 30◦, how tall is the lamppost?
  1. A 20-ft ladder leans against a building. If the base of the ladder is 10 ft from the base of the building, what is the angle of elevation of the ladder? How high does the ladder reach on the building?
  2. Prove the Pythagorean Identities:

(a) sin^2 θ + cos^2 θ = 1 (b) 1 + tan^2 θ = sec^2 θ (c) cot^2 θ + 1 = csc^2 θ

  1. Write the first trigonometric function in terms of the second for θ in the given quadrant.

(a) cos θ, sin θ; θ in QIII (b) cot θ, csc θ; θ in QII (c) sin θ, sec θ; θ in QIV

  1. If tan γ = − 1 2

for γ in QIV, find sin γ + cos γ.

  1. Find the period, phase shift, domain, range, and vertical asymptotes of the following functions.

(a) y = tan π 4

x (b) y = −4 sec

x +^5 π 6

(c) y = sec 2

x −

π 2

(d) y = −

3 csc^ π

x +

π 4

(e) y = tan

3 x^ −^

π 6

(f) y = − cot

2 x +

π 3