standard_description: Prove theorems about lines and angles. Theorems include: vertical angles are congruent; when a transversal crosses parallel lines, alternate interior angles are congruent and corresponding angles are congruent; points on a perpendicular bisector of a line segment are exactly those equidistant from the segment’s endpoints.
problem_activity: Warm-up
The purpose of this activity is for students to practice sketching spheres and labeling the radius and diameter of the sphere.
Launch
Give students 1–2 minutes of quiet work time, followed by a whole-class discussion.
Student Facing
Here is a method for quickly sketching a sphere:
Draw a circle.
Draw an oval in the middle whose edges touch the sphere.
[IMG]
Practice sketching some spheres. Sketch a few different sizes.
For each sketch, draw a radius and label it
\(r\)
.
Student Response
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Activity Synthesis
Invite students to share their sketches. Ask students to share what the diameter would look like if they did not already draw one in. Remind students that sketches can be used to help visualize a problem where an image might not be provided. In today’s lesson, they will be working with activities that might or might not have images provided and they should sketch or label any images provided to use as a tool to help understand the problem thoroughly.


aligns: no