Math Is Fun Forum

Monox D. I-Fly

Member

From: Indonesia

Registered: 2015-12-02

Posts: 2,000

[ASK] Proving Trigonometry Identity

If

, prove that

!
All I knew is that

, but I think it doesn't help in this case.

Last edited by Monox D. I-Fly (2019-12-01 14:35:07)

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Bob

Administrator

Registered: 2010-06-20

Posts: 10,619

Re: [ASK] Proving Trigonometry Identity

Are you sure this is the exact question?

From the RHS I got an expression close to the LHS but not the same.  So I tried to spreadsheet some values and did not get LHS = RHS.

eg.  If alpha = 30, beta = 60 and gamma = 90 then

LHS = 2x0.5 + 2 x root(3)/2 + 2x1 = 3  + root(3)

RHS = 4 x 0.5 x root(3)/2 x 1 = root(3)

Bob

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You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
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Monox D. I-Fly

Member

From: Indonesia

Registered: 2015-12-02

Posts: 2,000

Re: [ASK] Proving Trigonometry Identity

Well, this was a question asked by a student I am tutoring. He did say that he tried all angles to be 60° and the equation didn't match, so I told him that it means that it couldn't be proved.

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Actually I never watch Star Wars and not interested in it anyway, but I choose a Yoda card as my avatar in honor of our great friend bobbym who has passed away.
May his adventurous soul rest in peace at heaven.