SOLUTION: Let {{{a}}}, {{{b}}} and {{{c}}} be the sides of a triangle. If {{{a^2 + b^2 + c^2 = ab + bc + ca}}}, find the type of triangle it is.

Algebra ->  Triangles -> SOLUTION: Let {{{a}}}, {{{b}}} and {{{c}}} be the sides of a triangle. If {{{a^2 + b^2 + c^2 = ab + bc + ca}}}, find the type of triangle it is.      Log On


   



Question 1105372: Let a, b and c be the sides of a triangle. If a%5E2+%2B+b%5E2+%2B+c%5E2+=+ab+%2B+bc+%2B+ca, find the type of triangle it is.
Answer by ikleyn(52864) About Me  (Show Source):
You can put this solution on YOUR website!
.
If  a%5E2+%2B+b%5E2+%2B+c%5E2 = ab + ac + bc,  then


2%2A%28a%5E2+%2B+b%5E2+%2B+c%5E2%29 = 2*(ab + ac + bc),   or,  equivalently,


%28a-b%29%5E2+%2B+%28a-c%29%5E2+%2B+%28b-c%29%5E2 = 0,


which implies  a = b,  a = c  and  b = c.


Hence, the triangle is  EQUILATERAL.