a)

1. Find the gradient of AB.

2. Find the gradient perpendicular to that gradient.

3. Find the midpoint of AB

4. Use the point from 3. and the gradient fom 2. to get the perpendicular bisector of AB.

b)

1. Since this is an isosceles triangle, AC = BC. Use the distance formula:

c)

Use the distance formula again.

d)

1. You have the midpoint AB, label it X. Find the distance XC.

2. Now, use

Where base = AB, height = XC