Back to Prove triangles congruent — Problem 5 · Task Set 7

Exercises: Prove Triangles Congruent Using Rigid Motions

Work through each section in order. Show your reasoning where indicated.

Grade 9·20 problems·~35 min·Common Core Math - HS Geometry·standard·hsg-co-b-7

Work through problems with immediate feedback

Fluency Practice

Apply the biconditional and CPCTC directly.

In a geometric proof, a student writes: "By CPCTC, $\angle A = \angle D$ ." Which condition must have been established in a prior step for this conclusion to be valid?

Vertices $A$ and $D$ must be labeled with the same letter in the figure.

The triangles containing $\angle A$ and $\angle D$ must be congruent.

$\angle A$ and $\angle D$ must be corresponding angles of parallel lines.

The triangles must share a common side.