The area of the triangle, whose vertices are at the points (2, 1, 1), (3, 1,2) and (- 4,0, 1) is

∵Δyz=12y1z11y2z21y3z31,Δzx=12z1x11z2x21z3x31,Δxy=12x1y11x2y21x3y31∴ Δyz=121    1    11    2    10    1    1=12|[1(2−1)−1(1−0)+1(1−0)]|=12|[1−1+1]|=12Δzx=121212311−41=12|[1(3+4)−2(2−1)+1(−8−3)]|=12|[7−2−11]|=3Δxy=12211311−401=12|[2(1−0)−1(3+4)+1(0+4)]|=12Area of triangle,Δ=Δyz2+Δzx2+Δxy2=122+(3)2+122=14+9+14=382 sq unit