Mohon bantuannya dengan cara yang lengkap.

38. AB x AC
= (-1,-2,-1) x ( 3,-2,-2)
=(-3, 4,2)
=-3i + 4j + 2k
misal c =AB = b-a
=(-3,1,-2) - ( -2,3,-1)
=(-1,-2,-1)
|c|= √ (-1)^2 + (-2)^2 + (-1)^2
=√1 + 4 +1 =√6
misal b =AC = c-a
= ( 1, 1,-3) - ( -2,3,-1)
= (3,-2,-2)
|b|= √9 + 4 +4
=√17
39. luas segitiga ABC =1/2 x a x t
=1/2 x √17 x √17
= 1/2 x 17 = 8,5 cm2

mencari , misal a = BC = c-b
= (1,1,-3) - (-3,1,-2)
=( 4,0,-1)
|a| =√16 + 0 +1 =√17
#mungkin kayak gitu caranya. maaf kalo salah =-)