standard_description: Identify and describe relationships among inscribed angles, radii, and chords. Include the relationship between central, inscribed, and circumscribed angles; inscribed angles on a diameter are right angles; the radius of a circle is perpendicular to the tangent where the radius intersects the circle.
problem_activity: Find two values where
$${\mathrm{cos}x=-1}$$
.
What is
$${\mathrm{arccos}(-1)}$$
?


aligns: no