Oswego City School District
Regents Exam Prep Center: Parallel and Perpendicular Lines
This site displays formulas and examples, pertaining to slope, for parallel and perpendicular lines.
Purple Math
Purplemath: Slope: Parallel and Perpendicular Lines
Describes and gives good examples relating to the slopes of parallel and perpendicular lines.
Lawrence Hall of Science
The Math Page: Skill in Algebra: The Slope of a Straight Line
Here is a site that clearly and thoroughly explains many topics surrounding the slope of a line, including slope of horizontal, vertical, parallel, and perpendicular lines in addition to the formula and concept of slope. There are...
University of North Carolina
University of North Carolina Wilmington: Lines in a Plane
This site from the University of North Caroline at Wilmington provides great information on the lines in a plane. The information that is given is in-depth and complete, touching on the slope of a line, equations of lines, and linear...
Math Planet
Math Planet: Parallel and Perpendicular Lines
Provides examples and a video lesson that illustrates parallel and perpendicular lines.
Illustrative Mathematics
Illustrative Mathematics: G Gpe, G Srt Slope Criterion for Perpendicular Lines
The goal of this task is to use similar triangles to establish the slope criterion for perpendicular lines. Aligns with HSG-GPE.B.5 and HSG-SRT.B.5.
Illustrative Mathematics
Illustrative Mathematics: G Gpe, G Co, G Srt Unit Squares and Triangles
For this task, students are shown three unit squares and two line segments connecting two pairs of vertices. They are asked to find the area of a triangle formed by intersecting lines. They can solve it using coordinate geometry or...
Illustrative Mathematics
Illustrative Mathematics: G Gpe.5 Triangles Inscribed in Circle
In this task, students use ideas about linear functions to determine when certain angles are right angles. They use the fact that two lines (if not vertical or horizontal) are perpendicular when their slopes are inverse reciprocals, as...
Illustrative Mathematics
Illustrative Mathematics: G Gpe Equal Area Triangles on the Same Base Ii
This task has young scholars apply their knowledge of parallel lines to solve a geometric problem on areas of triangles. The task is open-ended in that students can choose their method of completing the task. Aligns with G-GPE.B.5.
Illustrative Mathematics
Illustrative Mathematics: G Gpe Equal Area Triangles on the Same Base I
This task is a relatively easy application of the formula for the area of a triangle and the use of parallel lines. Aligns with G-GPE.B.5.
Illustrative Mathematics
Illustrative Mathematics: G Gpe Parallel Lines in the Coordinate Plane
The goal of this task is to prove the slope criterion for parallel lines. Aligns with HSG-GPE.B.5.
Illustrative Mathematics
Illustrative Mathematics: G Gpe When Are Two Lines Perpendicular?
The goal of this task is to examine when two lines in the plane are perpendicular in terms of their slopes. Aligns with HSG-GPE.B.5.
Illustrative Mathematics
Illustrative Mathematics: G Gpe a Midpoint Miracle
For this task, learners are asked to draw a quadrilateral so that no two sides are congruent, no two angles are congruent, and no two sides are parallel. The task gives students the opportunity to prove that if we join the midpoints of a...
BBC
Bbc: Bitesize: Rectilinear Shapes
Find the gradient, equations and intersections of medians, altitudes and perpendicular bisectors using our knowledge of the mid-point as well as parallel and perpendicular lines.
Other
Central Michigan University: Point Slope Form
This resource features information on the point-slope form in geometry. It provides a good definition, several examples, and information on various forms.
CK-12 Foundation
Ck 12: Algebra: Families of Lines
[Free Registration/Login may be required to access all resource tools.] Find the equation of a line that is parallel or perpendicular to a given line.
CK-12 Foundation
Ck 12: Algebra: Equations of Perpendicular Lines
[Free Registration/Login may be required to access all resource tools.] This lesson covers determining if two lines are parallel, perpendicular, or neither and finding the equation of perpendicular lines to a given line.
CK-12 Foundation
Ck 12: Algebra: Equations of Perpendicular Lines
[Free Registration/Login may be required to access all resource tools.] Learn how to recognize and write equations of perpendicular lines.
CK-12 Foundation
Ck 12: Algebra: Comparing Equations of Parallel and Perpendicular Lines
[Free Registration/Login may be required to access all resource tools.] Use their slopes to determine if two lines are parallel or perpendicular.
CK-12 Foundation
Ck 12: Algebra: Determining the Equation of a Line
This comprehensive study guide highlights the main terms and formulas needed to determine the equation of a line. Examples are included.
CK-12 Foundation
Ck 12: Algebra: Lines in the Coordinate Plane Study Guide
This comprehensive study guide highlights the main terms and formulas needed to review lines in the coordinate plane. Examples are included.
CK-12 Foundation
Ck 12: Geometry: Lines in the Coordinate Plane Study Guide
This study guide on lines in a coordinate plane covers key terms, what different line slopes look like, postulates about parallel and perpendicular lines, the slope-intercept equation, how to graph parallel and perpendicular lines, and...
CK-12 Foundation
Ck 12: Geometry: Lines and Angles Study Guide
This study guide on lines and angles covers key terminology; line notation; parallel, perpendicular, and skew lines; and postulates and theorems about lines. It is available for download with free registration.
Cool Math
Coolmath: Perpendicular Lines
This CoolMath Resource will help students determine if lines are perpendicular by finding the slope, using the point-slope formula, and graphing.