This applet shows the construction of the circumcenter of a triangle.

Move points A, B and C and notice what happens to the triangle.
Answer the following questions:
a. What are the blue lines in the construction called?
b. How are those blue lines constructed?
c. What is point D called?
d. Constructing a circle outside triangle ABC is called what?
e. Where does point D lie when the triangle is right?
f. Where does point D lie when the triangle is acute?
g. Where does point D lie when the triangle is obtuse?
h. What is unique about the blue lines when all three sides of the triangle are congruent?