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# Blindsided

## What's the best way to position a car's mirrors?

Even under ideal conditions, driving is dangerous. To make the experience as safe as possible, cars come with a lot of mirrors to help drivers see what’s happening around them. So how do people typically position their car’s mirrors…and how should they position them?

In this lesson, students use reflections to model what drivers see in their rear-view and side-view mirrors. They see how adjusting the mirrors impacts the areas that drivers can see, and assess some common rules of thumb when it comes to the best way to orient your mirrors.

### REAL WORLD TAKEAWAYS

• A rear-view mirror should be angled slightly toward the driver in order to see the area directly behind the car.
• Side-view mirrors will provide the most helpful visibility if they’re positioned so that you cannot see the edge of your own car but so that you can see an adjacent car just out of the area reflected in the rear-view mirror.

### MATH OBJECTIVES

• Reflect rays off of a rear-view mirror using the law of reflection
• See how the area shown in a rear-view mirror changes when the driver adjusts the mirrors
• Reflect rays off of side-view mirrors using the law of reflection
• Assess the quality of rules of thumb for the best way to position your mirrors in a car

This complex task is best as a culminating unit activity after students have developed formal knowledge and conceptual understanding.
Expressions & Equations
Expressions & Equations
Content Standards G.CO.1 Know precise definitions of angle, circle, perpendicular line, parallel line, and line segment, based on the undefined notions of point, line, distance along a line, and distance around a circular arc. G.CO.4 Develop definitions of rotations, reflections, and translations in terms of angles, circles, perpendicular lines, parallel lines, and line segments. G.CO.5 Given a geometric figure and a rotation, reflection, or translation, draw the transformed figure using, e.g., graph paper, tracing paper, or geometry software. Specify a sequence of transformations that will carry a given figure onto another. G.CO.12 Make formal geometric constructions with a variety of tools and methods (compass and straightedge, string, reflective devices, paper folding, dynamic geometric software, etc.). Copying a segment; copying an angle; bisecting a segment; bisecting an angle; constructing perpendicular lines, including the perpendicular bisector of a line segment; and constructing a line parallel to a given line through a point not on the line.
Mathematical Practices MP.1 Make sense of problems and persevere in solving them. MP.4 Model with mathematics.