Question

Find the area of triangle formed by the pt. Origin, A(1,2,3) and B(-3,-2,-1)

Answer 1

area of triangle = 1/2 x matrix of X1 Y1 Z1
X1 Y2 Z2
1 1 1
=1/2 x 1. 2 3
-3 -2 -1
1 1 1
= 1/2 x [1(-2-1)-2(-3-1)+3(-3-2)]
= 1/2 x [-3+6-15]
= 1/2 x [-12].
= -6 unit²
but, area is always in positive...
so, area of triangle ABC = 6 unit ²