How to define and construct an angle bisector.
How to define a central angle and find the measure of its intercepted arc; how to describe the intercepted arcs of congruent chords.
How to find the angle between planes, and how to determine if two planes are parallel or perpendicular.
Understanding why the area of a triangle is 1/2 base times height
How to describe same side interior and same side exterior angles and their special properties.
How to derive the sine of a sum formula.
How to use inverse trig functions to find angles in right triangles.
How to define the sine ratio and identify the sine of an angle in a right triangle.
How to define the cosine ratio and identify the cosine of an angle in a right triangle.
How to define the tangent ratio and identify the tangent of an angle in a right triangle.