Students will first examine the relationship between the slopes of perpendicular lines by rotating line L1 and comparing the slopes m1 and m2.

In this setting, students can refine their conclusion by inputting specific values for m1 and viewing the corresponding values of m2.

Students are provided another look at the relationship between the slopes of two perpendicular lines, represented by triangles with a hypotenuse on each line and one leg of length 1 (corresponding to the definition of slope as “rise over run”).

In this problem, students use the relationship between slopes of perpendicular lines to observe that the radius of a circle and the corresponding tangent line are perpendicular.