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Geometry · Chapter 4 · Lesson 4.8 · Printable PDF

Proving the Base Angles Theorem Worksheet with Answer Key

6 problems on proving the base angles theorem: using angle bisectors and midpoints in isosceles triangles, equilateral triangles, finding errors, and converse proofs. 2 pages, with a worked answer key.

6 problems2 pagesanswer key
Printable Proving the base angles theorem worksheet with answer key - Geometry (Page 1 PDF preview)
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Try one first: a free Chapter 1 worksheet (PDF, no sign-in).

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What's on the worksheet

  1. Find y, AB, BC and an angle in an isosceles triangle with an angle bisector.
  2. Find AM and AB from the base and the area of an isosceles triangle.
  3. Find lengths and an angle in an equilateral triangle with an altitude.
  4. Check Kofi's proof that base angles are congruent.
  5. Prove two perpendicular segments from the midpoint are congruent.
  6. Prove a triangle with a bisector perpendicular to the base is isosceles.

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The free lesson teaches it with worked examples and practice problems.

Proving the base angles theorem: the lesson ›

More Chapter 4 worksheets: Triangle congruence and proof