Let be a triangle the position vectors of whose vertices are respectively and . Then, is 

a) 
Isosceles and right angled 
b) 
Equilateral 
c) 
Right angled but not isosceles 
d) 
None of these 
Let be a triangle the position vectors of whose vertices are respectively and . Then, is 

a) 
Isosceles and right angled 
b) 
Equilateral 
c) 
Right angled but not isosceles 
d) 
None of these 
(a)
We have,
and,
and
Clearly,
Hence, the triangle is right angled isosceles triangle