Subtract the first vertex from the other two, giving side <vectors> $(2,1)$ and $(3,4)$. Their <determinant> is $2\cdot4-3\cdot1=5$, the signed area of the corresponding <parallelogram>. The <triangle> occupies half that area, hence \b[its area is $5/2$]. Taking the absolute value would remove any sign change caused by reversing the vertex order. This is the <determinant formula for triangle area>.

Solution

Past exam of the year 1 of the computer science course of the University of Oxford / 2019 / Digital systems, linear algebra, introduction to formal proof resit / 4 / a / Solution

 Solution (source code)