This applet shows the construction of the orthocenter in 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 O called?
d. Where is point O when the triangle is acute?
e. Where is point O when the triangle is obtuse?
f. Where is point O when the triangle is right?
g. What is unique about the blue lines when all three sides of the triangle are congruent?