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# Baaasic Vectors. Determine the angles within a triangle

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Hey guys, I'm not posting this up so I don't have to do it, I've done all of the calculations and everything and have a pretty reasonable idea on what I'm doing, but I'm just getting wrong answers.

Triangle has 3 points (1, 0, 1), (6, 2, -7), (3, -2, 2).

I named my points A, B and C respectively.

I calculated AB, AC, BC and got

AB = (-5, -2, 7)

AC = (-2, 2, -1)

CB = (-3, -4, 9)

I then calculated magnitudes of each

||AB|| = sqrt 78

||AC|| = 3

||CB|| = sqrt 106

Dot Products were calculated aswell

AB.AC = 15

AC.CB = -7

AB.CB = 86

Cos(theta) = AB.AC / ||AB||.||AC||

Solved for theta and got 55.51

For AC and CB theta was 103.09

And finally AB and CB was 18.95

Which added up to approx 177 =/= 180.

So I don't know what I'm doing wrong? I thought I had all of my working correct?

If you guys could shed some light I'd greatly appreciate it, I dunno where I'm going wrong!?

Cheers,

Karl

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Just looking at it quickly AB should be (-5,-2,8) and not 7 in z-entry. Tell me, if that makes you get [math]180^\circ[/math]...

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