Question

Find the area of the triangle determined by the points p(2, −1, 0), q(3, 1, −1) and r(0, 1, 2)

Answer 1

We can calculate the length of pq=√(2-3)²+(-1-1)²+(0+1)²=√6
pr=√(2-0)²+(-1-1)²+(0-2)²= 2√3 and qr=√18= 3√2
Now we have cosinqpr= (6+12-18):(2.√6.2√3)=0 or this triangle is right at p
And the area is 1/2 x √6 x 2√3= 3√2