First, we find the vectors AB and AC. AB=B−A=(2+22−2,0−2,4−6)=(22,−2,−2) AC=C−A=(2+22−2,4−2,4−6)=(22,2,−2) Next, we find the cross product of these two vectors.
AB×AC=i^2222j^−22k^−2−2=i^((−2)(−2)−(−2)(2))−j^((22)(−2)−(−2)(22))+k^((22)(2)−(−2)(22)) =i^(4+4)−j^(−42+42)+k^(42+42)=8i^+0j^+82k^=(8,0,82) The magnitude of the cross product is
∣∣AB×AC∣∣=82+02+(82)2=64+0+64⋅2=64+128=192=64⋅3=83 The area of the triangle ABC is half the magnitude of the cross product.
Area=21∣∣AB×AC∣∣=21(83)=43