Question

If mnp has vertices at m (-5,-7) , N (7,-2) andcp (2,10) is mnp isoscles?

Answer 1

My graphing program shows two of the side lengths are the same.

ΔMNP IS isosceles.

Answer 2

Check the picture below.

now, clearly the longest side is MP, and for a triangle to be an isosceles, it has to have two equal sides, so two sides must be twins.

since MP is the longest one, that only leaves out NP and NM, are they twins?

$\bf ~~~~~~~~~~~~\textit{distance between 2 points}\\\\ \begin{array}{ccccccccc} &&x_1&&y_1&&x_2&&y_2\\ % (a,b) &N&(~ 7 &,& -2~) % (c,d) &P&(~ 2 &,& 10~) \end{array}\\\\\\ % distance value d = \sqrt{( x_2- x_1)^2 + ( y_2- y_1)^2} \\\\\\ NP=\sqrt{[2-7]^2+[10-(-2)]^2}\implies NP=\sqrt{(2-7)^2+(10+2)^2} \\\\\\ NP=\sqrt{(-5)^2+12^2}\implies NP=\sqrt{25+144}\implies \boxed{NP=13}$

and now let's check NM

$\bf ~~~~~~~~~~~~\textit{distance between 2 points}\\\\ \begin{array}{ccccccccc} &&x_1&&y_1&&x_2&&y_2\\ % (a,b) &N&(~ 7 &,& -2~) % (c,d) &M&(~ -5 &,& -7~) \end{array}~~~ \\\\\\ NM=\sqrt{[-5-7]^2+[-7-(-2)]^2}\\\\\\ NM=\sqrt{(-5-7)^2+(-7+2)^2} \\\\\\ NM=\sqrt{(-12)^2+(-5)^2}\implies NM=\sqrt{144+25}\implies \boxed{NM=13}$