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# Law of sines and trig question

Registered User regular
edited April 2007

okay, what am I doing wrong?

b0bd0d on

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Registered User regular
edited April 2007
SOH CAH TOA.

You know all the angles. You want to relate the hypotenuse to either x or y. Since sin and cos both relate to the hypotenuse (sin@ = opposite/hyptenuse and cos@ = adjacent/hypotenuse) you can use either of them.

So, sin45degrees = (root2) / x and sin45degrees = (root2)/y
You can see this from the graph, correct?

Just solve for the unknown variable. You know how to do that?

Al_wat on
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Registered User regular
edited April 2007
yeah, I know. y and x are one...so 1^2 and 1^2 equal...1? so sqr1 equals...1. So that means...the hypo is 1....but it's not. It's sqr2.

b0bd0d on
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Registered User regular
edited April 2007
a^2 + b^2 = c^2

so:

1^2 + 1^2 = ?

1 + 1 = 2

take square root of answer to find hypotenuse:

sqrt(2)

It's right.
One AND one is TWO.

Virum on
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Registered User regular
edited April 2007
If x and y are both one then the pythagorean theorem has the hypotenuse being sqrt(2).

x^2 + y^2 = h^2
1 + 1 = h^2
2 = h^2
h = sqrt(2)

Edit: beaten

Bob Sapp on
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Registered User regular
edited April 2007
aha!! Some i'm an idiot eh? stupid addition. YOU WIN AGAIN!
wait, what's the sqr of 2?

b0bd0d on
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Registered User regular
edited April 2007
The sqr of 2 is 4. The sqrt of 2 is an irrational number, so you can't write it, but it is approximately 1.41.

Smug Duckling on
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Registered User regular
edited April 2007
Also for future reference remember the unit circle. A 45 degree right triangle has a side to hypotenuse ratio of (sqrt(2)/2):1. A 60/30 degree triangle ratio is (1/2):1 (sqrt(3)/2):1.

And you should never use the law of sines and cosines to find measurements for a right triangle.

mrcheesypants on
Diamond Code: 2706 8089 2710
Oh god. When I was younger, me and my friends wanted to burn the Harry Potter books.

Then I moved to Georgia.
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Registered User regular
edited April 2007
why not? It's not correct? Explain, I'm interested.

b0bd0d on
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Major East CoastRegistered User regular
edited April 2007
No, but he was just saying there is an easier way, (IE the unit circle method he mentioned).
My advice is to just memorize those 3 configurations, you'll find them often enough.
Also, if you don't know the unit circle, just keep working this way. Better to learn one way 100% than 2 ways 1/2.

Iceman.USAF on
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Registered User regular
edited April 2007
no, what I'm asking is, why should you not use law of sines to find right angles? I got the unit circle memorized. That's not it. I'm actually wondering something but I think I'm doing something wrong to get the solution.

"The sqr of 2 is 4. The sqrt of 2 is an irrational number, so you can't write it, but it is approximately 1.41."
Yeah, but that triangle says it's 1...doesn't it?

b0bd0d on
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Registered User regular
edited April 2007
no, it really doesn't

Al_wat on