 | | From: | mina_world | | Subject: | drawing | | Date: | Sun, 23 Jan 2005 22:20:34 +0900 |
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 | hello.....doctor~
draw the ordered pair (x,y) in the x-y plane such that
cosx > (siny)*{sin(x+y)}
sorry...i don't know.
give me good hint, please.
thank you very much for your advice.
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| | From: | bryant_j_j at yahoo.com | | Subject: | Re: drawing | | Date: | 23 Jan 2005 05:36:29 -0800 |
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| use the trigonometric formula cos(x+y)-cos(x-y)=-2sin(x)sin(y) to make
things easier.
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| | From: | William Elliot | | Subject: | Re: drawing | | Date: | Sun, 23 Jan 2005 05:57:01 -0800 |
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| On Sun, 23 Jan 2005 bryant_j_j@yahoo.com wrote:
> use the trigonometric formula cos(x+y)-cos(x-y)=-2sin(x)sin(y) to make
> things easier.
>
Alsousespacestomakereadingeasier.
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| | From: | William Elliot | | Subject: | Re: drawing | | Date: | Sun, 23 Jan 2005 05:52:41 -0800 |
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| On Sun, 23 Jan 2005, mina_world wrote:
> draw the ordered pair (x,y) in the x-y plane such that
> cosx > (siny)*{sin(x+y)}
>
Let y = 0, x = pi/2
> sorry...i don't know.
> give me good hint, please.
>
Are you wanting to graph or draw the region
{ (x,y) | sin y * sin x+y < cos x } ?
sin y (sin x cos y + cos x sin y) < cos x
sin x sin y cos y + cos x sin^2 y < cos x
sin x sin y cos y + cos x - cos x * cos^2 y < cos x
sin x sin y cos y < cos x cos^2 y
For cos y > 0
sin x sin y < cos x cos y
For cos y < 0
sin x sin y > cos x cos y
For cos y = 0,
sin x sin y = 0
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| | From: | mina_world | | Subject: | Re: drawing | | Date: | Mon, 24 Jan 2005 00:15:28 +0900 |
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| thank you very much.
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