Find the angles of a triangle whose vertices are `A(0,-1,-2),B(3,1,4)` and `C` (5,7,1).

Explanation

Here, `vec(AB) = vecB - vecA = 3hati+2hatj+6hatk`

`vec(BC) = 2hati+6hatj-3hatk`

`vec(AC) = 5hati+8hatj+3hatk`

`|vec(AB)| = sqrt(3^2+2^2+6^2) = 7`

`|vec(BC)| = sqrt(32^2+6^2+(-3)^2) = 7`

`|vec(AC)| = sqrt(5^2+8^2+3^2) = 7sqrt2`

Now, `vec(AB)*vec(BC) = 6+12-18 = 0`

It means, `AB` and `BC` are perpendicular.

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