for (b) they want you to show that the perpendicular bisectors of the sides of a triangle, in this case OR, OQ, OP, all intersect at the same point, in this case O.
for (c) they want you to show that the lengths of a, b, c are all equal
ABC is a triangle as shown in the diagram below. P, Q and R are the midpoints of the sides BC, CA and AB respectively. O is the point of intersection of the perpendicular bisectors of CA and AB.
Let OA = a, OB = b and OC = c.
a) Prove that OP is perpendicular to BC.
This was pretty straightforward.
b) Hence prove that the perpendicular bisectors of the sides of a triangle are concurrent.
What is this question asking? I'm new to both proofs and vectors, so these types of questions are a challenge.
c) Prove that |a| = |b| = |c|.
EDIT: Forgot to add the diagram.