The Purplemath Forums

Hello everybody. I am now reading a russian book on high-maths from beginning and have an exercise for you:

prove that the triangle with its summits P(-2,-1), Q(6,1) and R(3,4) is right-angle.

have a luck:)

you are maybe right, but I didi not mean that, i.e. I had to put this exercise in the Linear Algebra section. The thing is that in this case we have to use a formula, describing a distance between to points. let's say if we have two points M1(x1,y1) and M2(x2,y2). and you have to use a distance form...