j_hallgren
Posts: 1427
Joined: Sun Jun 04, 2000 11:48 am

Need Help With Math Problem Related To Triangle.

Tue May 31, 2005 10:27 pm

It's been 30+ yrs since high school for me so...
Need to find out how long a side of a triangle would be:
Thus starting at point A, I walk straight ahead for 50 feet to point B. I then turn right (90 degrees) and go to unknown point C.
How far should I walk to get to C if the angle from point A to C is 20 degrees off from A to B? Does that description make sense? Thanks!
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redngold
Posts: 6673
Joined: Wed Mar 22, 2000 12:26 pm

RE: Need Help With Math Problem Related To Triangle.

Tue May 31, 2005 10:31 pm

Here's all you need to know:

The Pythagorean Theorem (applies only to right triangles): a^2 + b^2 = c^2

and: All the angles of a triangle must add up to 180 degrees, if you're trying to figure out the degree of angle.
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MD11Engineer
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Joined: Sun Oct 26, 2003 5:25 am

RE: Need Help With Math Problem Related To Triangle.

Tue May 31, 2005 10:35 pm

Quickly I would say:

Alpha = Angle between AC and AB
AB = distance A to B

BC = distance B to C

BC = tan (Alpha) * AB



Jan
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j_hallgren
Posts: 1427
Joined: Sun Jun 04, 2000 11:48 am

RE: Need Help With Math Problem Related To Triangle.

Tue May 31, 2005 10:38 pm

The problem with the application of P-T to this issue is that I only know the length of side A! And I need the length of side B, not the angle of the third corner, which I knew to be 70 degrees.

I also don't have any reference material to get the value of tangent for this issue, and search for it turns up way too many items.

[Edited 2005-05-31 15:41:38]
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SLC1
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Joined: Thu Dec 02, 2004 2:13 pm

RE: Need Help With Math Problem Related To Triangl

Tue May 31, 2005 10:43 pm

if memory serves me correctly, and i understand your question, your length BC=50*sin20/sin70, which ultimately comes to 18.191851171331 this is because sin A/BC = sin B/AC = sin C/AB

[Edited 2005-05-31 15:46:30]
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FLYtoEGCC
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Joined: Thu Feb 12, 2004 7:56 am

RE: Need Help With Math Problem Related To Triangle.

Tue May 31, 2005 10:47 pm

You know the angle BAC to be 20 degrees.

Tan (angle) = opposite side / adjacent side

So if your unknown side BC = x, you would do:

Tan 20 = x / 50

So x = 50 * Tan 20

Which should give you an answer of 18.19851171 ft...
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redngold
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Joined: Wed Mar 22, 2000 12:26 pm

RE: Need Help With Math Problem Related To Triangle.

Tue May 31, 2005 10:48 pm

Argggh I didn't read the question well enough... Definitely need the sines and tangents here...
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j_hallgren
Posts: 1427
Joined: Sun Jun 04, 2000 11:48 am

RE: Need Help With Math Problem Related To Triangle.

Tue May 31, 2005 10:51 pm

Tried Google with different phrase and found:
http://www.pangolin.com/userhelp/scanangles.htm
Which deals with scanner and screen but gives the formula and value of Tangent for 20 deg as .364

Edit: I was posting this at same time FlytoEgc did so didn't see that reply but THANKS to all who helped me!  Smile

[Edited 2005-05-31 15:58:48]
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