Is sin(10) Irrational? Proving the Irrationality of sin(10) in Degrees

In summary, the conversation discusses proving the irrationality of sin(10) in degrees through contradiction. The suggested method involves supposing sin(10) is rational and finding a polynomial it satisfies, then showing it has no rational roots.
  • #1
SrEstroncio
62
0

Homework Statement


Prove [itex] \sin{10} [/itex], in degrees, is irrational.


Homework Equations


None, got the problem as is.


The Attempt at a Solution


Im kinda lost.
 
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  • #2
SrEstroncio said:

Homework Statement


Prove [itex] \sin{10} [/itex], in degrees, is irrational.


Homework Equations


None, got the problem as is.


The Attempt at a Solution


Im kinda lost.

Okay, are you familiar with proof by contradiction?

Start by contradicting the statement :

Suppose that sin(10) is irrational.
 
  • #3
SrEstroncio said:

Homework Statement


Prove [itex] \sin{10} [/itex], in degrees, is irrational.


Homework Equations


None, got the problem as is.


The Attempt at a Solution


Im kinda lost.

Let x=sin(10). You'll want to find a polynomial x satisfies and show it has no rational root. Hint: sin(30)=1/2=sin(10+10+10).
 
  • #4
I should suppose sin(10) is rational, if i am to contradict the statement, shouldn't i?
 
  • #5
yes and that means that sin(10) can be represented by the ratio of two integers a and b sin(10) = a/b

next step...
 
  • #6
SrEstroncio said:
I should suppose sin(10) is rational, if i am to contradict the statement, shouldn't i?

Zondrina's hint contains nothing of any real substance to start solving the problem. Mine does. I suggest you start trying it.
 

What is the definition of an irrational number?

An irrational number is a real number that cannot be represented as a ratio of two integers. This means that it cannot be written as a fraction with a non-zero denominator.

What is the proof that sin(10) is irrational?

The proof that sin(10) is irrational is based on the fact that if a number is a rational number, then its sine must also be a rational number. However, since sin(10) is not a rational number, it follows that it is irrational.

Why is it important to prove that sin(10) is irrational?

Proving that sin(10) is irrational is important because it helps to deepen our understanding of the properties of irrational numbers and their relationship with other mathematical concepts. It also has implications in other fields, such as physics and engineering, where trigonometric functions are used.

Is there a general method for proving the irrationality of trigonometric functions?

Yes, there is a general method for proving the irrationality of trigonometric functions. This method is based on the fact that if a trigonometric function is rational, then its argument (in this case, 10) must also be rational. By showing that the argument is irrational, we can prove that the trigonometric function is also irrational.

Can the irrationality of sin(10) be proven using only elementary mathematics?

Yes, the irrationality of sin(10) can be proven using only elementary mathematics. The proof involves basic concepts such as the definition of an irrational number, the properties of rational and irrational numbers, and the trigonometric identities for sin(2x) and sin(5x). It does not require advanced mathematical concepts or techniques.

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