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Need Help With Math Problem Related To Triangle.

J_Hallgren From United States, joined Jun 2000, 1506 posts, RR: 0
Posted (4 years 6 months 2 days 12 hours ago) and read 357 times:

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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7 replies: All unread, jump to last

Redngold From United States, joined Mar 2000, 6907 posts, RR: 58
Reply 1, posted (4 years 6 months 2 days 12 hours ago) and read 354 times:

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 From Germany, joined Oct 2003, 10367 posts, RR: 67
Reply 2, posted (4 years 6 months 2 days 12 hours ago) and read 352 times:

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

J_Hallgren From United States, joined Jun 2000, 1506 posts, RR: 0
Reply 3, posted (4 years 6 months 2 days 12 hours ago) and read 348 times:

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 From , joined Dec 1969, posts, RR:
Reply 4, posted (4 years 6 months 2 days 12 hours ago) and read 343 times:

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]

FLYtoEGCC From United Kingdom, joined Feb 2004, 947 posts, RR: 4
Reply 5, posted (4 years 6 months 2 days 12 hours ago) and read 337 times:

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 From United States, joined Mar 2000, 6907 posts, RR: 58
Reply 6, posted (4 years 6 months 2 days 12 hours ago) and read 333 times:

Argggh I didn't read the question well enough... Definitely need the sines and tangents here...

Borderline Personality Disorder - it's not just for fence sitters. (Slogans courtesy of friends in psych rotations)

J_Hallgren From United States, joined Jun 2000, 1506 posts, RR: 0
Reply 7, posted (4 years 6 months 2 days 12 hours ago) and read 331 times:

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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