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Area (in sq. units) of the triangle with vertices A (1,1,1) B (1,2,3) and C (2,3,1) is:

Solution

✅ Correct Option: 1

Here AB⃗=(0,1,2)\vec{AB} = (0,1,2) and AC⃗=(1,2,0)\vec{AC} = (1,2,0).

Their cross product is (−4,2,−1)(-4,2,-1), with magnitude 16+4+1=21\sqrt{16+4+1} = \sqrt{21}.

Area =12∣AB⃗×AC⃗∣=1221= \dfrac{1}{2}|\vec{AB}\times\vec{AC}| = \dfrac{1}{2}\sqrt{21} sq. units.

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