If cos(pi*n) = (-1)^n is cos(-pi*n) = (-1)^n

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In summary, the conversation is about a student solving a Fourier series integral and needing help with understanding if cos(pi*n) and cos(-pi*n) are equal. The student believes they are equal due to the even nature of the cosine function, and they are confirmed to be correct.
  • #1
mrmerchant786

Homework Statement


i wassolving a Fourier series integral, and needed some help
if cos(pi*n) = (-1)^n is cos(-pi*n) = (-1)^n ?

Homework Equations


i think it is because cos is an even function so -x of the function should still remain the same, becuase if you look at the graph and flip it its still the same graph

if someone could reply to confirm my thoughts or tell me why its wrong, that would be great thanks :)

The Attempt at a Solution

 
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  • #2
mrmerchant786 said:

Homework Statement


i wassolving a Fourier series integral, and needed some help
if cos(pi*n) = (-1)^n is cos(-pi*n) = (-1)^n ?

Homework Equations


i think it is because cos is an even function so -x of the function should still remain the same, becuase if you look at the graph and flip it its still the same graph

if someone could reply to confirm my thoughts or tell me why its wrong, that would be great thanks :)

The Attempt at a Solution


you are correct because ##\cos (x) = \cos (-x)##.
 
  • #3
Buffu said:
you are correct because ##\cos (x) = \cos (-x)##.
thanks :smile:, thought so
 

FAQ: If cos(pi*n) = (-1)^n is cos(-pi*n) = (-1)^n

1. What is the definition of "cos(pi*n) = (-1)^n"?

The definition of "cos(pi*n) = (-1)^n" is a mathematical equation that states the cosine of any multiple of pi is equal to either 1 or -1, depending on whether the multiple is an even or odd number. This can also be written as "cos(n*pi) = (-1)^n".

2. How is cos(pi*n) related to (-1)^n?

Cos(pi*n) and (-1)^n are related because they both represent a pattern of either 1 or -1 depending on the value of n. This means that when n is an even number, both expressions will equal 1, and when n is an odd number, both expressions will equal -1.

3. Can the equation "cos(pi*n) = (-1)^n" be applied to any number?

No, this equation can only be applied to multiples of pi. This is because pi is a special number in mathematics that represents the ratio of a circle's circumference to its diameter. It is an irrational number and cannot be expressed as a fraction, so it can only be multiplied by whole numbers to create multiples of pi.

4. Does cos(-pi*n) have the same value as cos(pi*n)?

Yes, cos(-pi*n) has the same value as cos(pi*n) because they both represent the cosine of a multiple of pi. The only difference is that one is a positive multiple of pi (pi*n) and the other is a negative multiple of pi (-pi*n), but the cosine function is symmetrical and will give the same value for both.

5. How is the equation "cos(pi*n) = (-1)^n" used in mathematics?

The equation "cos(pi*n) = (-1)^n" is used in mathematics to simplify and solve trigonometric equations and identities. It is also used in the study of periodic functions and can be applied in various fields of science and engineering, such as signal processing and wave analysis.

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