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Glossary
Cavalieri’s principle
If two solids are cut into cross sections by parallel planes, and the corresponding cross sections on each plane always have equal areas, then the two solids have the same volume.
Parallel Postulate
The Parallel Postulate says that given a line and a point not on the line, there is one and only one line through that is paralell to .
altitude
An altitude in a triangle is a line segment from a vertex to the opposite that is perpendicular to the that side.
angle bisector
A line through the vertex of an angle that divides it into two equal angles.
apex
The highest point of a pyramid when it is sitting on its base.
arc
The part of a circle lying between two points on a circle.
arc length
The length of an arc.
arccos
The arccos of a number between 0 and 1 is the acute angle whose cosine is that number.
arcsin
The arcsin of a number between 0 and 1 is the acute angle whose sine is that number.
arctan
The arccos of a positive number 1 is the acute angle whose tangent is that number.
auxiliary line
An extra line drawn in a gure to reveal hidden structure.
axis of rotation
A line about which you rotate a two-dimensional gure to get a three-dimensional gure.
central angle
The angle formed by the two radii to the endpoints of an arc.
chord
A chord of a circle is a line segment both of whose endpoints are on the circle.
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Teacher Guide