Problem preview

G-SRT.2 Warmup M2-047-A07-V01

Use similarity transformations to decide similarity and explain angle equality and side proportionality in triangles.

Find a missing angle or variable from corresponding angles in similar triangles

Problem

Use triangle similarity to find the missing angle: triangle \(ABC\) is similar to triangle \(DEF\), and angle \(A=42^{\circ}\). Find angle \(D\).

Unworked paired or staged triangle geometry showing only the supplied evidence.

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What this problem is really about

Corresponding angles in similar triangles are equal, but the written triangle order must identify the correct pair first. We’ll expand the first-second-third vertex mapping, locate the requested angle’s partner, transfer the known measure through angle congruence, and check that the response names the requested angle with degree units.

Answer choices

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angle D = 42 degrees

angle D = 138 degrees

angle D = 65 degrees

angle D = 48 degrees

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Curriculum context

Course: Math II
Standard: G-SRT.2
Category: Geometry
Domain: Similarity, Right Triangles, and Trigonometry
Objective: Use similarity transformations to decide similarity and explain angle equality and side proportionality in triangles.
Problem type: Find a missing angle or variable from corresponding angles in similar triangles