Florida B.E.S.T. MA.912.GR.1

MA.912.GR.1 is a B.E.S.T. standard. These are the benchmarks under it.

• MA.912.GR.1.1

  Prove relationships and theorems about lines and angles. Solve mathematical and real-world problems involving postulates, relationships and theorems of lines an...

• MA.912.GR.1.2

  Prove triangle congruence or similarity using Side-Side-Side, Side-Angle-Side, Angle-Side-Angle, Angle-Angle-Side, Angle-Angle and Hypotenuse-Leg.

• MA.912.GR.1.3

  Prove relationships and theorems about triangles. Solve mathematical and real-world problems involving postulates, relationships and theorems of triangles.

• MA.912.GR.1.4

  Prove relationships and theorems about parallelograms. Solve mathematical and real-world problems involving postulates, relationships and theorems of parallelog...

• MA.912.GR.1.5

  Prove relationships and theorems about trapezoids. Solve mathematical and real-world problems involving postulates, relationships and theorems of trapezoids.

• MA.912.GR.1.6

  Solve mathematical and real-world problems involving congruence or similarity in two-dimensional figures.

01

What Students Need to Do

Students use definitions, postulates, and known theorems to build logical arguments about geometric figures. They also use those results to find missing measures and solve diagram-based problems.

02

What Mastery Looks Like

Students choose a relevant theorem and verify that its conditions fit the diagram. They write a logical proof with supported steps, then use the proven relationship to calculate an unknown measure or justify a conclusion.

03

Common Misconceptions

Students may treat a diagram as proof, assuming lines are parallel or angles are equal because they look that way. They may use the result they are trying to prove, skip reasons, or apply a theorem when its conditions are not met.

04

How to Assess It

Exit ticket: In triangle ABC, D is the midpoint of AB and E is the midpoint of AC. Prove DE is parallel to BC, then find BC if DE = 6.

1. 01

   Have pairs fold paper triangles to mark midpoints, measure the connecting segment, state a conjecture, then prove it.

2. 02

   Ask students to explain which step fails in a flawed vertical angles proof and rewrite that step with a valid reason.

3. 03

   Run a proof-card race where teams arrange statements and reasons for congruence, parallel-line, and circle theorems.

4. 04

   Give a roof-truss diagram and ask students to prove two braces congruent before calculating a missing length.

• MA.912.GR.4

  Use geometric measurement and dimensions to solve problems.

• MA.912.GR.3

  Use coordinate geometry to solve problems or prove relationships.