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Transcript
4.3 Graphing Other Trigonometric Functions The tangent function: f x = tan x 2 -5 - 3 2 - - 2 2 3 5 2 2 -2 The tangent function exhibits the following properties: - It’s period is - For all x, tan (-x) = - tan x. It is an odd function. - Its graph is symmetric with respect to the origin. 𝜋 - Its domain: the tangent is undefined at all odd multiples of and has vertical asymptotes 𝜋 2 at every line with equation 𝑥 = (2𝑘 + 1) ; 𝑘 ∈ 𝑍 - Its range is the set of all real numbers, . Its zeros occur at multiples of . 2 Advanced Mathematics/Trigonometry: 4.3 Graphing Other Trigonometric Functions Page 1 The cotangent function: f(x) = cot x 2 -2 -5 - 3 2 - - 2 2 3 5 2 2 -2 The cotangent function exhibits the following properties: - It’s period is - For all x, cot (-x) = - cot x. It is an odd function. - Its graph is symmetric with respect to the origin. - Its domain: the cotangent is undefined at all multiples of and has vertical asymptotes at every line with equation x k ; k Z - Its range is the set of all real numbers, . 𝜋 - Its zeros occur at odd multiples of . 2 Advanced Mathematics/Trigonometry: 4.3 Graphing Other Trigonometric Functions Page 2 Example 1: Graph each function. 1 a. 𝑦 = tan 𝑥 2 y 6 5 4 3 2 1 -3 - 5 -2 2 - 3 - 2 - 2 2 -1 x 3 2 2 5 3 2 -2 -3 -4 -5 -6 1 b. 𝑦 = tan 𝑥 3 y 6 5 4 3 2 1 -3 - 5 2 -2 - 3 2 - - 2 -1 2 x 3 2 2 5 3 2 -2 -3 -4 -5 -6 Advanced Mathematics/Trigonometry: 4.3 Graphing Other Trigonometric Functions Page 3 c. 𝑦 = tan 3𝑥 y 4 3 2 1 - 2 - 3 - 6 -1 6 3 2 x -2 -3 -4 For the functions 𝑓(𝑥) = 𝑎 tan 𝑏(𝑥 − 𝑐) + 𝑑 and 𝑔(𝑥) = 𝑎 cot 𝑏(𝑥 − 𝑐) + 𝑑, the constants a, b, c, and d affect the graphs. Since amplitude does not apply to these functions, a vertically dilates the graph, period is 𝜋 |𝑏| , phase shift is |𝑐| (to the left if c < 0 and to the right if c > 0) and vertical shift is |𝑑| (downward if d < 0 and upward if d > 0). Advanced Mathematics/Trigonometry: 4.3 Graphing Other Trigonometric Functions Page 4 Example 2: Determine the period, phase shift, vertical shift, and the equations of at least two vertical asymptotes of each. Then graph. 𝜋 a. 𝑓(𝑥) = 2 tan (𝑥 − ) + 3 6 y x b. 𝑓(𝑥) = cot(2𝑥 − 𝜋) y x Advanced Mathematics/Trigonometry: 4.3 Graphing Other Trigonometric Functions Page 5 Example 3: Derive an equation with the given characteristics then graph each. a. cotangent: period 𝜋 2 , phase shift 𝜋 4 left y x 𝜋 𝜋 2 4 b. tangent: period , phase shift left y x Advanced Mathematics/Trigonometry: 4.3 Graphing Other Trigonometric Functions Page 6 The secant function: y = sec x 2 y = cos x -2 -5 - 3 - 2 - 2 2 3 5 2 2 -2 -4 The secant function exhibits the following properties: - It’s period is 2 - For all x, sec (-x) = sec x. It is an even function. - Its graph is symmetric with respect to the y-axis. 𝜋 - Its domain: the secant is undefined at all odd multiples of and has vertical asymptotes 𝜋 2 at every line with equation 𝑥 = (2𝑘 + 1) ; 𝑘 ∈ 𝑍 - Its range is (-, -1] [1, ) 2 Advanced Mathematics/Trigonometry: 4.3 Graphing Other Trigonometric Functions Page 7 The cosecant function: 4 2 y= csc x y = sin x -2 -5 - 3 2 - - 2 2 3 5 2 2 -2 -4 The cosecant function exhibits the following properties: - It’s period is 2 - For all x, csc (-x) = - csc x. It is an odd function. - Its graph is symmetric with respect to the origin. - Its domain: the cosecant is undefined at all multiples of and has vertical asymptotes at every line with equation x k ; k Z - Its range is (-, -1] [1, ) Advanced Mathematics/Trigonometry: 4.3 Graphing Other Trigonometric Functions Page 8 Example 4: Graph each function. 1 a. 𝑦 = −2 sec 𝑥 2 y x 1 b. 𝑦 = 4 sec 𝑥 4 y x Advanced Mathematics/Trigonometry: 4.3 Graphing Other Trigonometric Functions Page 9 1 c. 𝑦 = csc 3𝑥 2 y x For the functions 𝑓(𝑥) = 𝑎 sec 𝑏(𝑥 − 𝑐) + 𝑑 and 𝑔(𝑥) = 𝑎 csc 𝑏(𝑥 − 𝑐) + 𝑑 , the constants a, b, c, and d affect the graphs. Since amplitude does not apply to these functions, a vertically dilates the graph, period is 2𝜋 |𝑏| , phase shift is |𝑐| (to the left if c < 0 and to the right if c > 0) and vertical shift is |𝑑| (downward if d < 0 and upward if d > 0). Advanced Mathematics/Trigonometry: 4.3 Graphing Other Trigonometric Functions Page 10 Example 5: Find the period, phase shift, vertical shift, and the equations of at least two vertical asymptotes of each. Then graph. a. 𝑦 = csc (4𝑥 + 3𝜋 2 )−1 y x b. 𝑦 = sec(2𝑥 − 𝜋) + 2 y x Advanced Mathematics/Trigonometry: 4.3 Graphing Other Trigonometric Functions Page 11 Homework: pp. 205 – 206: Practice Exercises 1, 4, 7, 8, 10, 12, 14, 17, 19 (day 1) pp. 206 – 207: Practice Exercises 21 – 23; 34, 37, 39 (day 2) pp. 205 – 207: Practice Exercises 11, 13, 15, 35 (day 3) pp. 205 – 207: Practice Exercises 2, 3, 5, 36, 38 (day 4) Advanced Mathematics/Trigonometry: 4.3 Graphing Other Trigonometric Functions Page 12