The graph of a sinusoidal function has a maximum point at (0,10) and then intersects its midline at (pi/4,4). Write the formula of the function, where x is entered in radians. f(x)=

Respuesta :

Answer: y = 6 cos (2x) + 4

Step-by-step explanation:

A cosine function is expressed as: y = A cos (Bx - C) + D   where

  • amplitude (A) is the distance from the midline to the max/min.
  • B = 2π/P  where P is the period
  • C/B is the phase shift
  • D is the center line (aka midline)

A = Max - Midline

   = 10 - 4

   = 6

The max to the midpoint is π/4

⇒ 1/4 P = π/4

⇒ P = π

B = 2π/P    

  = 2π/π

  = 2

C = 0 because there is no phase shift

D = 4 (given)

Input A = 6, B = 2, C = 0, and D = 4 into the cosine function:

y = 2 cos (2x - 0) + 4

There is a family of sinusoidal functions of the form:

[tex]y = 4 + 6\cdot \cos [(2+4\cdot i)\cdot x], \forall \,i \in \mathbb{Z}[/tex]

Where [tex]i[/tex] is associated to the angular frequency of a function within the family.

In this case, the sinusoidal function reaches the upper bound when [tex]x = 0[/tex] and the middle value when [tex]x = 0.25\pi[/tex]. We should find all coefficients contained in the following sinusoidal model:

[tex]y = (y_{max}-y_{mid})\cdot \cos A\cdot x + B[/tex] (1)

Where:

  • [tex]x[/tex] - Independent value.
  • [tex]y[/tex] - Dependent value.
  • [tex]y_{mid}[/tex] - Midpoint value.
  • [tex]y_{max}[/tex] - Upper bound value.
  • [tex]A[/tex] - Period coefficient.
  • [tex]B[/tex] - Translation coefficient.

If we know that [tex]y_{mid} = 4[/tex], [tex]y_{max} = 10[/tex], [tex](x_{1},y_{1}) = (0, 10)[/tex] and [tex](x_{2}, y_{2}) = \left(\frac{\pi}{4}, 4 \right)[/tex], then we have the following system of equations:

[tex]6+ B = 10[/tex] (2)

[tex]6\cdot \cos \frac{\pi\cdot A}{4} + B = 4[/tex] (3)

By (2):

[tex]B = 4[/tex]

By (3):

[tex]6\cdot \cos \frac{\pi\cdot A}{4} = 0[/tex]

[tex]\cos \frac{\pi\cdot A}{4} = 0[/tex]

[tex]\frac{\pi\cdot A}{4} = \cos ^{-1} 0[/tex]

[tex]A = \frac{4}{\pi}\cdot \cos^{-1}0[/tex]

[tex]A = \frac{4}{\pi}\cdot \left(\frac{\pi}{2}+\pi\cdot i \right)[/tex], [tex]\forall \,i\in\mathbb{Z}[/tex]

[tex]A = 2 +4\cdot i[/tex], [tex]\forall \,i \in \mathbb{Z}[/tex]

There is a family of sinusoidal functions of the form:

[tex]y = 4 + 6\cdot \cos [(2+4\cdot i)\cdot x], \forall \,i \in \mathbb{Z}[/tex] (4)

Where [tex]i[/tex] is associated to the angular frequency of a function within the family.

We kindly invite to check this question on sinusoidal functions: https://brainly.com/question/12060967

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