Free Printable WorksheetMathGeometryMath CurriculumG-CO.C.10

GEO.58 Congruence in isosceles and equilateral triangles Worksheet

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Worksheet Overview & Skills Covered

Core academic competencies and curriculum alignment

This Geometry Math worksheet provides structured practice on GEO.58 Congruence in isosceles and equilateral triangles. Students are guided through targeted exercises that build foundational understanding, computational accuracy, and critical thinking skills.

GEO.58 Congruence in isosceles and equilateral triangles - Primary standard selected for prompt fields in this prompt cell: CCSS G-CO.C.10. Skill statement in this prompt cell: Identify the congruent parts in an isosceles or equilateral triangle diagram and select the correct unknown measure. Associated standards listed with this skill in the curriculum source: CCSS G-CO.C.10; FL MA.912.GR.1.3; MA G-CO.C.10; NY GEO G.G-CO.C.10; TEKS §111.41(c); CCSS G-CO.B.6-8; NY GEO G.G-CO.B; FL MA.912.GR.2.6. Use this prompt-provided wording as the supporting standard description for this workflow.

Whether you are an educator preparing classroom handouts, a tutor reinforcing weekly topics, or a parent supporting homeschool learning, this printable resource gives students the deliberate practice required to achieve subject fluency and master state standards.

Grade

Geometry

Subject

Math

Domain

Math Curriculum

Formats

PDF & DOCX

Sample Practice Problems

Preview the types of problems and questions covered in this worksheet

Below are sample questions representative of the exercises included on this worksheet and related GEO.58 Congruence in isosceles and equilateral triangles skill assessments:

Problem 1Difficulty: Mastery
A diagram contains equilateral triangle ABC and isosceles triangle ACD sharing side AC. In triangle ABC, AC = 18 units. In triangle ACD, AC = AD. What is AD?
A9 units
B18 units
C36 units
DCannot be determined
Solution & Explanation:The equilateral triangle gives AC = 18 units. In triangle ACD, AC and AD are congruent, so AD must also be 18 units.
Problem 2Difficulty: Mastery
In isosceles triangle ABC, sides AB and BC are congruent. Angle A measures 56 degrees. What is angle B?
A56 degrees
B68 degrees
C84 degrees
D112 degrees
Solution & Explanation:If AB = BC, then the base is AC, so base angles A and C are congruent. Angle C = 56 degrees. Angle B = 180 - 56 - 56 = 68 degrees.
Problem 3Difficulty: Mastery
In an isosceles triangle, the vertex angle is 12 degrees less than twice a base angle. What is the vertex angle?
A48 degrees
B72 degrees
C84 degrees
D96 degrees
Solution & Explanation:Let each base angle be b. The vertex angle is 2b - 12. Use b + b + (2b - 12) = 180, so 4b = 192 and b = 48. The vertex angle is 2(48) - 12 = 84 degrees.

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Frequently Asked Questions

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QWhat grade level and standards does this worksheet align with?

This worksheet is designed specifically for Geometry Math students. It aligns with educational standard G-CO.C.10 (Primary standard selected for prompt fields in this prompt cell: CCSS G-CO.C.10. Skill statement in this prompt cell: Identify the congruent parts in an isosceles or equilateral triangle diagram and select the correct unknown measure. Associated standards listed with this skill in the curriculum source: CCSS G-CO.C.10; FL MA.912.GR.1.3; MA G-CO.C.10; NY GEO G.G-CO.C.10; TEKS §111.41(c); CCSS G-CO.B.6-8; NY GEO G.G-CO.B; FL MA.912.GR.2.6. Use this prompt-provided wording as the supporting standard description for this workflow.).

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