How to define a tangent line; how to determine the angle a radius to a tangent forms.
How to find the length of tangent segments drawn to a circle from the same point.
How to define the tangent ratio and identify the tangent of an angle in a right triangle.
How to prove that an angle inscribed in a semicircle is a right angle; how to solve for arcs and angles formed by a chord drawn to a point of tangency.
How to use inverse trig functions to find angles in right triangles.
How to define a secant; how to find the length of various secants in circles.