Trigonometry sin cos Question

  • Thread starter basty
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  • #1
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I know that ##\sin^2 x + cos^2 x = 1.##

Is this mean that

##\sin^2 2x + \cos^2 2x = 1##

or

##\sin^2 3x + \cos^2 3x = 1##

or

##\sin^2 4x + \cos^2 4x = 1##

and so on?
 

Answers and Replies

  • #2
22,089
3,289
Yes.
 
  • #3
34,279
5,915
I know that ##\sin^2 x + cos^2 x = 1.##

Is this mean that

##\sin^2 2x + \cos^2 2x = 1##

or

##\sin^2 3x + \cos^2 3x = 1##

or

##\sin^2 4x + \cos^2 4x = 1##

and so on?
##sin^2(\text{whatever}) + cos^2(\text{whatever}) = 1##
The "whatever" in both places has to be the same, of course.
 
  • #4
95
0
Does ##\sin^2 2x = \frac{1 - \cos 4x}{2}?##
 
  • #5
34,279
5,915
Does ##\sin^2 2x = \frac{1 - \cos 4x}{2}?##
##\sin^2(A) = \frac{1 - \cos(2A)}{2}##
If A = 2x, what is 2A?
 

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