A line is a straight path that extends infinitely in both directions. It is represented by a straight line with arrows at each end to indicate that it continues indefinitely.

- Straight Line: A line that does not bend or curve.
- Ray: A part of a line that has one endpoint and extends indefinitely in one direction.
- Line Segment: A part of a line that has two endpoints and a definite length.

An angle is formed by two rays or line segments that share a common endpoint, called the vertex of the angle.

- Acute Angle: An angle that measures less than 90 degrees.
- Right Angle: An angle that measures exactly 90 degrees.
- Obtuse Angle: An angle that measures more than 90 degrees but less than 180 degrees.
- Straight Angle: An angle that measures exactly 180 degrees.
- Reflex Angle: An angle that measures more than 180 degrees but less than 360 degrees.

Angles have several properties that are important to understand:

- Vertical Angles: When two lines intersect, the angles opposite each other are called vertical angles and are congruent.
- Adjacent Angles: Two angles that share a common side and vertex, but do not overlap.
- Complementary Angles: Two angles whose measures add up to 90 degrees.
- Supplementary Angles: Two angles whose measures add up to 180 degrees.

Here are some key points to remember for studying lines and angles:

- Understand the different types of lines and their properties.
- Be able to identify and classify different types of angles.
- Recognize the properties of angles, such as vertical angles, adjacent angles, complementary angles, and supplementary angles.
- Practice drawing and measuring angles using a protractor.

Study GuidePlane Figures: Lines and Angles Activity LessonSupplementary angles Activity LessonComplementary Angles Worksheet/Answer key

Plane Figures: Lines and Angles Worksheet/Answer key

Plane Figures: Lines and Angles Worksheet/Answer key

Plane Figures: Lines and Angles

Geometry (NCTM)

Analyze characteristics and properties of two- and three-dimensional geometric shapes and develop mathematical arguments about geometric relationships.

Precisely describe, classify, and understand relationships among types of two- and three-dimensional objects using their defining properties.

Create and critique inductive and deductive arguments concerning geometric ideas and relationships, such as congruence, similarity, and the Pythagorean relationship.

Measurement (NCTM)

Understand measurable attributes of objects and the units, systems, and processes of measurement.

Understand, select, and use units of appropriate size and type to measure angles, perimeter, area, surface area, and volume.

Apply appropriate techniques, tools, and formulas to determine measurements.

Select and apply techniques and tools to accurately find length, area, volume, and angle measures to appropriate levels of precision.

Connections to the Grade 7 Focal Points (NCTM)

Data Analysis: Students use proportions to make estimates relating to a population on the basis of a sample. They apply percentages to make and interpret histograms and circle graphs.