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gyanshrestha

Member

Registered: 2007-11-06

Posts: 41

Helop me to prove this trigonometry identity

Sorry for mistake Here is corrected questions

Last edited by gyanshrestha (2011-12-13 03:42:48)

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Bob

Administrator

Registered: 2010-06-20

Posts: 10,164

Re: Helop me to prove this trigonometry identity

hi gyanshrestha

Wow!  That's a nasty one.  But I'm thinking of simplifying

for the three values of A to put in later.

I'll come back to this if I get anywhere.

Bob

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Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

Bob

Administrator

Registered: 2010-06-20

Posts: 10,164

Re: Helop me to prove this trigonometry identity

hi again,

Some progress:

note:

so

You'd think that is simple enough to finish the identity .... but, I'm still working on it.  Phew! 

Bob

Last edited by Bob (2011-12-12 07:30:04)

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Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

Bob

Administrator

Registered: 2010-06-20

Posts: 10,164

Re: Helop me to prove this trigonometry identity

Hang on a minute.

To be an identity it must be true for all x.

Put x = 60 degrees.  3x = 180  9x = 540 '=' 180  27x = 1620 '=' 180

so

LHS = 2sin60/cos180 + 2sin180/cos180 + 2sin 180/cos 180 = √3/-1 + 0 + 0 = -√3

RHS = tan180 + tan60 = 0 + √3 = √3

Bob

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Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

gyanshrestha

Member

Registered: 2007-11-06

Posts: 41

Re: Helop me to prove this trigonometry identity

thanks Bob

I made a mistake in the question. corrected question is

I also edited Initial post.

I check the identity for x=1,2,3, 4 and they all are true.

thanks

but is still not getting to proof.

Last edited by gyanshrestha (2011-12-13 03:47:48)

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http://gyan.talkacademy.com.np