geometry
posted by Luke Phillips .
The coordinates of the vertices of a triangle are A(1,3), B(6,10), and C(11,18). Find the perimeter of the triangle when the coordinates are multiplied by 3.

The distance between A and B can be calculated using the distance formula:
distance(A,B)=sqrt((xbxa)^2+(ybya)^2)
=sqrt((16)^2+(310)^2)
=sqrt(25+49)
=sqrt(74)
=8.602 approx.
You can find similarly the distances BC and CA.
Add up the sum AB+BC+CA which is the perimeter of the original triangle.
For the triangle with coordinates 3 times shown, multiply the original perimeter by 3.