The cosine model is y = - 7 + 10 · cos (π · x/30 - π).
The sine model is y = - 7 + 10 · sin (π · x/30 - π/2).
How to find sinusoidal functions from a given graph
Sinusoidal functions are periodic trascendent expressions which involves trigonometric functions. There are two kinds of sinusoidal functions:
[tex]y = A \cdot \cos (B\cdot x + C) + D[/tex] (1)
[tex]y = A\cdot \sin (B\cdot x + C) + D[/tex] (2)
Where:
- A - Amplitude
- B - Angular frecuency
- C - Angular phase
- D - Midpoint
First, we find the amplitude and the midpoint:
A = [3 - (- 17)]/2
A = 10
D = [3 + (- 17)]/2
D = - 7
Now we find the angular phase and the angular frequency for each model:
Cosine model (x, y) = (0, - 17), (x, y) = (30, 3)
- 17 = 10 · cos C - 7 (3)
3 = 10 · cos (30 · B + C) - 7 (4)
By (3):
- 10 = 10 · cos C
cos C = - 1
C = acos(- 1)
C = - π
And by (4):
3 = 10 · cos (30 · B - π) - 7
10 = 10 · cos (30 · B - π)
cos (30 · B - π) = 1
30 · B - π = acos 1
30 · B - π = 0
30 · B = π
B = π/30
The cosine model is y = - 7 + 10 · cos (π · x/30 - π).
Sine model
Obtain the sine model by using trigonometric expressions:
cos θ = sin (θ + π/2) (5)
By (5):
y = - 7 + 10 · sin (π · x/30 - π + π/2)
y = - 7 + 10 · sin (π · x/30 - π/2)
The sine model is y = - 7 + 10 · sin (π · x/30 - π/2).
To learn more on sinusoidal functions: https://brainly.com/question/12060967
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