Trigonometric Graphs And Equations
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Trigonometric Graphs
- Trig graphs are the graphs of y = sin x, y = cos x, and y = tan x for angles from 0° to 360°.
- They have periodic shapes and symmetries that are essential to know.
- The period of sin x and cos x is 360°; the period of tan x is 180°.
Graph of y = sin x
- Oscillates between 1 and -1; passes through (0,0).
- Key points: (0°,0), (90°,1), (180°,0), (270°,-1), (360°,0).
- The graph is symmetric about the origin (odd function).
Graph of y = sin x
Graph of y = cos x
- Oscillates between 1 and -1; y-intercept at (0,1).
- Key points: (0°,1), (90°,0), (180°,-1), (270°,0), (360°,1).
- y = cos x is a translation of y = sin x by 90° to the left.
Graph of y = cos x
Graph of y = tan x
- Consists of branches separated by asymptotes at x = 90°, 270°, etc.
- Passes through (0,0); each branch goes from -∞ to +∞.
- Period is 180°; key points: (0°,0), (45°,1), (135°,-1), (180°,0), (225°,1), (315°,-1), (360°,0).
Graph of y = tan x
Solving Trig Equations
- Use the inverse trig function on a calculator to find the first solution.
- Use the graph of the trig function to find additional solutions within the given interval (usually 0° ≤ x ≤ 360°).
- For sin x = k: if x is an acute solution, then 180° - x is the obtuse solution.
- For cos x = k: if x is a solution, then 360° - x is the other solution.
- For tan x = k: if x is a solution, then x + 180° is another solution.
- Always check solutions by substituting back into the original equation.
Solving sin x = 0.5 using symmetry

Rearranging Trig Equations
- Equations may need rearranging first, e.g., 2 sin x - 1 = 0 becomes sin x = 1/2.
- Then solve using the standard method for the basic trig equation.
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Câu hỏi luyện tập
Xem trước miễn phí — 8 trên 64 câu hỏi. Đăng ký để xem tất cả.
1.What is the period of the graph of y = sin x?
Easy- A90°
- B180°
- C360°
- D720°
2.What is the y-coordinate of the point where the graph of y = cos x crosses the y-axis?
Easy- A0
- B1
- C-1
- D0.5
3.The graph of y = tan x has asymptotes at which x-values in the range 0° ≤ x ≤ 360°?
Easy- A0° and 180°
- B90° and 270°
- C180° and 360°
- D0° and 360°
4.If sin x° = 0.36, find the acute angle x.
Easy- A21.1°
- B36.0°
- C0.36°
- D69.0°
5.If sin x° = 0.36, find the obtuse angle x in the range 0° ≤ x ≤ 360°.
Medium- A158.9°
- B201.1°
- C338.9°
- D21.1°
6.Solve tan x = 2 for 0° ≤ x ≤ 360°. Give the two solutions.
Medium- A63.4° and 243.4°
- B63.4° and 116.6°
- C26.6° and 206.6°
- D63.4° and 296.6°
7.Solve 3 tan x = -4 for 0° ≤ x ≤ 360°. Give the two solutions.
Medium- A126.9° and 306.9°
- B53.1° and 233.1°
- C126.9° and 233.1°
- D53.1° and 306.9°
8.x° is an obtuse angle and sin x° = 0.43. Find the value of x.
Medium- A25.5°
- B154.5°
- C205.5°
- D334.5°
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