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#1 2010-07-07 12:02:01
Need some help, might need trig
Well, I want ot find two sides of a right-angled triangle, like this:
y
___
| /
x| / z
|/
I know what z is, but how do I calcuate the other two?
Also, x continues upwards, and y continues to the left.
Any help would be appreciated.
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#2 2010-07-07 12:10:12
Re: Need some help, might need trig
you need to know the angle between y and z or x and z as well.
http://en.wikipedia.org/wiki/Triangle#Using_trigonometry
will help you calculate it. jump to "trigonometry"
and please get on dropbox!
Last edited by sparks (2010-07-07 12:10:37)
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#3 2010-07-07 12:20:46
Re: Need some help, might need trig
sparks wrote:
you need to know the angle between y and z or x and z as well.
http://en.wikipedia.org/wiki/Triangle#Using_trigonometry
will help you calculate it. jump to "trigonometry"
and please get on dropbox!
The angles change depending on the length of z though, don't they? And that will change...
Anyway, can you e-mail me the password for dropbox please?
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#6 2010-07-07 12:29:47
Re: Need some help, might need trig
Sperry wrote:
Well, I want ot find two sides of a right-angled triangle, like this:
y
___
| /
x| / z
|/
Y can only be one length.
and with z being it's length, already known to you, x and y can only have one possible length.
There's some easy way of doing it, but I forget it.
): sorry.
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did you get the email? can you log in?#13 2010-07-08 09:26:43
Re: Need some help, might need trig
Sperry wrote:
nXIII wrote:
Are both x and y of variable (not constant) length?
They are both a fraction of a variable that changes.
if they are always the same fraction then they can be calculated from the variable.
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#14 2010-07-08 09:49:44
Re: Need some help, might need trig
You can try: ___________
hypotenuse (z) = \/ x^2 + y^2 if you have two lenghts. Because the equations you are trying to solve have 3 or more varaibles you need to know at least two to solve it.
My site Find someone post count. Click posts under username. Find number of pages. Times that by 40 for min and 60 for max and you have a rough estimate of post count.
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#16 2010-07-08 17:32:17
Re: Need some help, might need trig
3d rectangle? Use projection algorithms:
x = x * c / x
y = y * c / z
and rotation algorithms:
about x axis:
y = y * cos(theta) - z * sin(theta)
z = y * sin(theta) + z * cos(theta)
about y axis:
x = x * cos(theta) - z * sin(theta)
z = x * sin(theta) + z * cos(theta)
about z axis:
x = x * cos(theta) - y * sin(theta)
y = x * sin(theta) + y * cos(theta)
...I think.
Last edited by nXIII (2010-07-08 17:33:02)
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#17 2010-07-08 17:45:32
- johnnydean1
- Scratcher
- Registered: 2010-02-12
- Posts: 1000+
Re: Need some help, might need trig
^ I believe they are correct
You can now reach me on Twitter @johnnydean1_
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#18 2010-07-08 23:17:19
Re: Need some help, might need trig
Sperry wrote:
sparks wrote:
yes, you need to know at least one side and one angle to calculate anything else about a right-angle triangle.
well, xy is 90 degrees I know that...
One angle other than the right angle. 
In order to determine any triangle, you need three of
the six values (three sides, three angles), including at least one side (because with only the three angles you can scale the triangle to whatever size you want). You know one angle (the right angle) and one side (the hypotenuse). You need one more side or one more angle. (Actually just so someone doesn't call me on this, if you know two sides and an angle that isn't the one between the two sides, then there are two different-shaped possible triangles.)
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