91Ó°ÊÓ

Two congruent intersecting circles \(B\) and \(D\) (not shown) have a line (segment) of centers \(B D\) and a common chord \(A C\) that are congruent. Explain why quadrilateral \(A B C D\) is a square.

Suppose that a circle is divided by points \(A, B, C,\) and \(D\) into four congruent arcs. What is the measure of each arc? If these points are joined in order, what type of quadrilateral results?

Two congruent circles, \(\odot O\) and \(\odot P,\) do not intersect. Construct a common external tangent for \(\odot O\) and \(\odot P\).

Write a paragraph proof. An angle inscribed in a semicircle is a right angle.