Math Is Fun Forum

Identity

Member

Registered: 2007-04-18

Posts: 934

exact value

Find the exact value of

Is there a way to do this without drawing a triangle, what's the most efficient way? The book doesn't say which way it should be done.

Also, when finding

using triangles, you could have opp/adj = 2/-1 or opp/adj = -2/1 ... so couldn't there be 2 possible solutions?

Last edited by Identity (2008-12-24 21:29:59)

luca-deltodesco

Member

Registered: 2006-05-05

Posts: 1,470

Re: exact value

Trying both roots, the positive is correct, the negative incorrect

...

infact, it turns out that you must take the negative root, if x is negative, and the positive root if x is positive

Last edited by luca-deltodesco (2008-12-24 22:28:06)

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Identity

Member

Registered: 2007-04-18

Posts: 934

Re: exact value

Wow, very nice ! Thanks luca

Daniel123

Member

Registered: 2007-05-23

Posts: 663

Re: exact value

I think it's much quicker/easier/nicer to draw a triangle. The identities luca's used all come from triangles anyway.

Monox D. I-Fly

Member

From: Indonesia

Registered: 2015-12-02

Posts: 2,000

Re: exact value

I think it's much quicker/easier/nicer to draw a triangle. The identities luca's used all come from triangles anyway.

Agree. By looking at the sine value, we know that the height is 4 and the hypotenuse is 5. Thus, with the Pythagorean theorem we know that the base is 3.

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