3D Algebra/Geometry - Help?

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<p>3-Dimensions were really underrepresented in my algebra and geometry classes. I'm not talking about solid geometry, but about x,y,z coordinates and information to that extent. For example, I learned outside of class that for the midpoint of 2 (x,y,z) coords, you do the same as normal, but add (z1+z2)/2. And for the distance, you also just add (z2-z1)^2. I'm afraid that a different type of question will come, and I won't be able to answer it. </p>

<p>Does anybody know any other 'common' 3D type problems and the solutions to them? I know this isn't necessarily specific to the ACT, but a question might come up - and I want to be able to answer it; I'm aiming very high and that one question can dramatically affect my score. If anyone can help, by either explaining some new 3D idea, or linking to a site that covers 3D-related math. </p>

<p>Thank you :)</p>

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<p>yeah those always trick me too. i'm not sure. try google and find some equations for distance, etc. thats what i'm doing. ill post the urls on here if i find someting.
good luck tomorrow</p>

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<p><a href="http://en.wikipedia.org/wiki/Distance%5B/url%5D"&gt;http://en.wikipedia.org/wiki/Distance&lt;/a&gt;&lt;/p>

<p>scroll down a little bit, i would have copied it here but it's a .jpg not text</p>

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<p>I already know the distance and the midpoint formulas for 3D, but I'm wondering if there are any new things you might know? My wording probably confused you, sorry :P</p>

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<p><a href="http://www.answers.com/topic/plane-geometry%5B/url%5D"&gt;http://www.answers.com/topic/plane-geometry&lt;/a&gt;&lt;/p>

<p>This has some interesting stuff about 3D geometry (middle-bottom of page). Though some of the stuff is too complicated to be on ACT :P</p>