## Common Core Standards Questions G-CO.9

I have a number of questions about the CCSSM standards, and EXACTLY what they mean. Exactly what skill are the students expected to learn? What depth of understanding (or Depth of Knowledge, if you’re familiar with the DOK system) will be required of students?

Here’s my first one from high school Geometry:

G-CO.9 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.

I find standards like this frustrating. The basic standard itself is fairly vague: Prove theorems about lines and angles. Well heck, there’s a lot of those. The standard goes on to list as examples three particular theorems which are covered by most Geometry courses. Is this meant to be an exhaustive list? Are any other “theorems about lines and angles” going to be fair game?

What exactly are students going to be expected to do? Literally just prove these three theorems? If two angles are vertical angles then they are congruent? Or will this be buried as a step in a more involved problem?

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