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#1 2008-11-23 21:23:49

tony123
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cos(x - y)

Prove that if

and
,
then

Last edited by tony123 (2008-11-23 21:30:46)

#2 2008-11-24 10:23:59

JaneFairfax
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Re: cos(x - y)

Easy!

Q: Who wrote the novels Mrs Dalloway and To the Lighthouse?

#3 2008-11-24 10:27:04

Daniel123
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Re: cos(x - y)

By inspection,

Last edited by Daniel123 (2008-11-24 10:27:22)

#4 2008-11-24 10:49:28

JaneFairfax
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Re: cos(x - y)

You need to do a bit more work than that.

Q: Who wrote the novels Mrs Dalloway and To the Lighthouse?

#5 2008-11-25 08:16:32

greenisfab88
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Re: cos(x - y)

I have troublr with that too.
i need help!

#6 2008-11-25 12:50:06

JaneFairfax
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Re: cos(x - y)

By the way, you also need the condition

to ensure that
and
are not both
.

Q: Who wrote the novels Mrs Dalloway and To the Lighthouse?

#7 2010-01-23 14:58:56

jonecox
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Re: cos(x - y)

I know very well this expression.I am studying this function in school.I like your work.Thanks for share this information.

#8 2010-09-06 23:17:29

sameer mishra
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Re: cos(x - y)

cosx +cosy=a
sinx-siny=b
squarring bot the equation then subtrac
cos2x+cos2y+2cox(x-y)=a2-b2
2cos(x-y)[1+cos(x+y)]=a^2-b^2  (o)

now squarring above equation then add
cos(x+y)a^2+b^2)/2-1
now put the valu of cos(x+y) in (o)
cos(x-y)=a2 -b2/a2+b2

#9 2010-09-17 20:54:26

sameer mishra
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Re: cos(x - y)

hello JaneFairfax i think that you are intresested in trigo.
but i challange you in trigo. calculus algebra. coordinate pleaseeeeeeeee
accept my challenge and ask question from me