20190428, 11:54  #1 
Jul 2014
3×149 Posts 
something I think is true but can't prove
Hi,
does anyone know if sinAcosx  sinxcosA = 0 is true if and only if sinA = sinx and cosx = cosA are true? I've tried to prove it. I don't think I can. My mind's not working right anyway. I thought some help with this might help me straighten my head out a bit. (it would be appreciated). 
20190428, 12:19  #2  
Undefined
"The unspeakable one"
Jun 2006
My evil lair
189E_{16} Posts 
Quote:
And you get this: EF  EF = 0 

20190428, 12:32  #3 
Dec 2012
The Netherlands
1761_{10} Posts 
sin(A)cos(x)  cos(A)sin(x)=sin(Ax)
and sin(Ax)=0 if and only if Ax is an integer multiple of π. Good luck with your head! 
20190429, 19:55  #4 
Jul 2014
3×149 Posts 
thanks.

20190430, 22:18  #5 
∂^{2}ω=0
Sep 2002
República de California
2^{2}×3×7×139 Posts 
Or, in terms the way the OP phrased it, tan x = tan A if sin x = sin A and cos x = cos A, or if sin x = sin A and cos x = cos A.
Last fiddled with by ewmayer on 20190430 at 22:19 
20190430, 22:45  #6  
If I May
"Chris Halsall"
Sep 2002
Barbados
10011101000100_{2} Posts 
Quote:


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