Math Problem Statement

Grafik fungsi dibawah adalah y = -2 cos(kx - α) + dan -90° <= α <= 90°. Maka nilai dari C - K cos 5α

Solution

The image shows a trigonometric function problem. The function is given as y=2cos(kxα)y = -2 \cos(kx - \alpha), and the problem appears to ask for the values of CKcos5αC - K \cos 5\alpha.

Steps to solve the problem:

  1. Identify the amplitude, period, and phase shift:

    • The general form y=Acos(kxα)y = A \cos(kx - \alpha) is a cosine function with:
      • A=2A = -2: The amplitude (absolute value of AA) is 2, and since it's negative, the graph is reflected vertically.
      • kk: The angular frequency affects the period, which is 2πk\frac{2\pi}{k}.
      • α\alpha: This is the phase shift (in degrees or radians).
  2. Amplitude: From the graph, the maximum value is 5 and the minimum is 1. This suggests that the amplitude of the function has been shifted vertically.

  3. Period: From the graph, the distance between two crests (one full period) seems to be from 6060^\circ to 210210^\circ, meaning the period of the function is 21060=150210^\circ - 60^\circ = 150^\circ. Therefore: Period=360k=150\text{Period} = \frac{360^\circ}{k} = 150^\circ Solving for kk: k=360150=2.4k = \frac{360^\circ}{150^\circ} = 2.4

  4. Phase Shift: The phase shift is given by α\alpha, which shifts the graph horizontally. From the graph, it seems the function begins at 6060^\circ, so α=60\alpha = 60^\circ.

  5. Vertical Shift: Given that the graph's maximum is at 5 and minimum is at 1, the function has been shifted upwards by 3 units.

Thus, the equation of the function should be: y=2cos(2.4x60)+3y = -2 \cos(2.4x - 60^\circ) + 3

  1. Final step: Solve for CKcos(5α)C - K \cos(5\alpha):

    • Here, CC likely refers to the vertical shift, which is 3.
    • K=2K = 2 (from the amplitude), and α=60\alpha = 60^\circ.

    So: CKcos(5α)=32cos(5×60)=32cos(300)C - K \cos(5\alpha) = 3 - 2 \cos(5 \times 60^\circ) = 3 - 2 \cos(300^\circ) Using cos(300)=0.5\cos(300^\circ) = 0.5, we get: CKcos(5α)=32×0.5=31=2C - K \cos(5\alpha) = 3 - 2 \times 0.5 = 3 - 1 = 2

Thus, the value of CKcos(5α)C - K \cos(5\alpha) is 2.


Do you want more details or have any questions?

Here are 5 related questions:

  1. How does the value of kk affect the period of the cosine function?
  2. What is the significance of a vertical shift in trigonometric functions?
  3. How do you calculate the phase shift for a cosine function?
  4. Why is the amplitude taken as the absolute value of AA?
  5. What is the relationship between angular frequency and the period of a function?

Tip: For trigonometric functions, the period is always calculated as 2πk\frac{2\pi}{k} (in radians) or 360k\frac{360^\circ}{k} (in degrees).

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Math Problem Analysis

Mathematical Concepts

Trigonometry
Cosine function
Amplitude
Phase Shift
Periodicity

Formulas

y = A cos(kx - α)
Period = 360° / k
C - K cos 5α

Theorems

Cosine function properties
Amplitude and period relationships in trigonometric functions

Suitable Grade Level

Grades 10-12