Combining Sine and Cosine Functions for f-g: Homework Example

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In summary, the task is to find a sine function, f, and a cosine function, g, that can be written in the form of f-g, given the equation y = sqrt2sin(pi(x-2.25)). This can be achieved by using the identity sin(a-b)= sin(a)cos(b)-cos(a)sin(b) and substituting in constants A, B, w, and v for f(x) and g(x).
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Homework Statement


Determine a sine function, f, and a cosine function, g, such that y = sqrt2sin(pi(x-2.25))
can be written in the form of f-g.

Homework Equations


(f-g)(x) = f(x) - g(x)

The Attempt at a Solution


I think that you should sub in the y= equation so that you get:
sqrt2sin(pi(x-2.25)) = f(x) - g(x)

and then sub in any X value? I really don';t know
 
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  • #2
Do you understand what the question is asking? You are to find a function f(x)= A sin(wx) and a function g(x)= B cos(vx) for constants A, B, w, and v. Since you don't yet know what f and g are, putting values of x into what you have won't tell you anything.

What you need is the identity sin(a- b)= sin(a)cos(b)- cos(a)sin(b). That way, sin(pi(x- 2.25)= sin(pix- 2.25pi)= sin(pix)cos(2.25pi)- cos(pix)sin(2.25pi), a constant times a sine function of x and a constant times a cosine function of x.
 
  • #3
Sorry for my ignorance, I understand what you explained previously, but I don't understand what I get for f(x) and g(x)?
 

Related to Combining Sine and Cosine Functions for f-g: Homework Example

1. What are sine and cosine functions?

Sine and cosine are two trigonometric functions commonly used in mathematics and physics. Sine (sin) is defined as the ratio of the length of the side opposite an angle in a right triangle to the length of the hypotenuse, while cosine (cos) is defined as the ratio of the length of the adjacent side to the hypotenuse.

2. What is the purpose of combining sine and cosine functions?

The combination of sine and cosine functions allows for the creation of more complex functions that can better model real-world phenomena. By combining these functions, we can create functions with varying amplitudes, periods, and phases.

3. How do you combine sine and cosine functions?

To combine sine and cosine functions, we use the sum and difference identities for sine and cosine. These identities allow us to express functions such as f(x) = sin(x) + cos(x) or g(x) = sin(x) - cos(x), which can be further manipulated and simplified.

4. What is the difference between f-g and f(x) - g(x)?

f-g and f(x) - g(x) both represent the difference between two functions, but they are not the same. f-g represents the function obtained by subtracting g from f, while f(x) - g(x) represents the value of the difference between the two functions at a specific value of x.

5. How can combining sine and cosine functions be useful in real-life applications?

Combining sine and cosine functions is useful in many fields, such as physics, engineering, and signal processing. These functions can be used to model periodic phenomena, such as sound and light waves, and to analyze and predict their behavior. They are also used in the design of electronic circuits and in the study of oscillatory motion.

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