let's say
A(-3,1) B(-3,5) C(4,1)
we need to find the perimeter of ABC for that we find each of the sides
AB BC and AC
there is a formula to find the distance between 2 poins
let's say that a point has the structure A(x1,y1) where x=-3 and y=1 and B(x2,y2) where x2=-3 and y2=5
AB=[tex]\sqrt{(x2-x1)^2+(y2-y1)^2}[/tex]
AB=[tex]\sqrt{(-3+3)^2+(5-1)^2}[/tex]
AB=[tex]\sqrt{0^2+4^2}[/tex]
AB=4
we do the same thing for AC and BC
AC=[tex]\sqrt{(4+3)^2+(1-1)^2}[/tex]
AC=[tex]\sqrt{7^2+0^2}[/tex]
AC=7
BC=[tex]\sqrt{(4+3)^2+(1-5)^2}[/tex]
BC=[tex]\sqrt{7^2+(-4)^2}[/tex]
BC=[tex]\sqrt{49+16}[/tex]
BC=[tex]\sqrt{65}[/tex]
The perimeter is equal to the sum of the sides
P=AB+AC+BC=4+7+[tex]\sqrt{65}[/tex]=11+[tex]\sqrt{65}[/tex]
