Author note — to cover

Base angles opposite the equal sides are equal: find angles from a given apex or base angle, including the two-answer case where the given angle could sit in either position. The congruence proof of the fact lives on Proofs using congruent triangles. Both tiers. (G4, G6)

• Fluency — direct questions on base angles of an isosceles triangle, limited to this lesson's stated scope (4 questions).
• Application — use the same skill in unfamiliar or contextual questions without introducing a later method (4 questions).
• Check — questions built around the exclusions and likely misconceptions named in the lesson brief (4 questions).