A base is a specific face of a prism or pyramid.

A prism has 2 identical bases that are parallel. A pyramid has 1 base.

A prism or pyramid is named for the shape of its base.

Complementary angles have measures that add up to 90\(^\circ\).

For example, a \(15^\circ\) angle and a \(75^\circ\) angle are complementary.

A cross-section is the new face that is seen when a three-dimensional figure is sliced.

A rectangular pyramid is sliced parallel to the base. The cross-section is a smaller rectangle.

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A prism is a type of polyhedron with 2 bases that are identical and parallel. The bases are connected by parallelograms.

Here are some drawings of prisms.

A pyramid is a type of polyhedron that has 1 base. All the other faces are triangles that meet at a single vertex.

Here are some drawings of pyramids.

A right angle is half of a straight angle. It measures 90 degrees.

A straight angle is an angle that forms a straight line. It measures 180 degrees.

Supplementary angles have measures that add up to 180\(^\circ\).

For example, a \(15^\circ\) angle and a \(165^\circ\) angle are supplementary.

The surface area of a polyhedron is the number of square units that covers all of its faces with no gaps or overlaps.

For example, the 6 faces of a cube each have an area of 9 cm². So, the surface area of the cube is \(6 \boldcdot 9\), or 54 cm².

Vertical angles are opposite angles that share the same vertex. They are formed when two lines cross each other. Their angle measures are equal.

Angles \(AEC\) and \(DEB\) are vertical angles. If angle \(AEC\) measures \(120^\circ\), then angle \(DEB\) must also measure \(120^\circ\).

Angles \(AED\) and \(BEC\) are another pair of vertical angles.

Volume is the number of cubic units that fill a three-dimensional region with no gaps or overlaps.

This rectangular prism has 3 layers that are each 20 units³. So, the volume of the prism is 60 units³.