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Applying the Angle Theorems (Geometry)

Free printable Geometry geometry worksheet: apply the vertical angles, parallel lines, triangle angle sum, and isosceles base angles theorems to find missing angle measures.

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Geometry · Math worksheet
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Applying the Angle Theorems

Use the Vertical Angles Theorem, the parallel-lines-and-transversal theorems, the Triangle Angle Sum Theorem, and the Isosceles Triangle Base Angles Theorem to find each missing angle.

  1. 1.
    Two lines intersect, forming two pairs of vertical angles. One angle measures 124°. Use the Vertical Angles Theorem to find the measure of the angle vertically opposite it.
  2. 2.
    Two lines intersect, forming two pairs of vertical angles. One angle measures 132°. Use the Linear Pair Postulate to find the measure of an angle adjacent to it.
  3. 3.
    Two lines intersect, forming two pairs of vertical angles. One angle measures 106°. Use the Vertical Angles Theorem to find the measure of the angle vertically opposite it.
  4. 4.
    Two parallel lines are cut by a transversal. One interior angle measures 72°. Use the Alternate Interior Angles Theorem to find the measure of its alternate interior angle.
  5. 5.
    Two parallel lines are cut by a transversal. One angle measures 143°. Use the Corresponding Angles Postulate to find the measure of its corresponding angle at the other intersection.
  6. 6.
    Two parallel lines are cut by a transversal. One interior angle measures 118°. Use the Alternate Interior Angles Theorem to find the measure of its alternate interior angle.
  7. 7.
    A triangle has interior angles of 39° and 25°. Use the Triangle Angle Sum Theorem to find the third angle.
  8. 8.
    A triangle has interior angles of 52° and 74°. Use the Triangle Angle Sum Theorem to find the third angle.
  9. 9.
    A triangle has interior angles of 70° and 37°. Use the Triangle Angle Sum Theorem to find the third angle.
  10. 10.
    An isosceles triangle has a vertex (apex) angle of 40°. Use the Isosceles Triangle Base Angles Theorem and the Triangle Angle Sum Theorem to find each base angle.
  11. 11.
    An isosceles triangle has a base angle of 33°. Use the Isosceles Triangle Base Angles Theorem and the Triangle Angle Sum Theorem to find the other base angle and the vertex (apex) angle.
  12. 12.
    An isosceles triangle has a vertex (apex) angle of 82°. Use the Isosceles Triangle Base Angles Theorem and the Triangle Angle Sum Theorem to find each base angle.
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