Points, Lines, and Angle Relationships
Review the undefined terms, angle classifications, and the angle rules created by parallel lines and transversals.
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Questions Covered in This Set
12 cards to master
What are the three undefined terms in geometry?
Point, line, and plane — they can't be defined without using equally vague words.
Difference between a segment and a ray?
A segment has two endpoints and a measurable length; a ray has one endpoint and extends forever through the second point (order matters).
Angle Addition Postulate
If D is in the interior of ∠ABC, then m∠ABD + m∠DBC = m∠ABC.
Complementary vs. supplementary angles
Complementary angles sum to 90°; supplementary angles sum to 180°. (C before S, 90 before 180.)
What is a linear pair, and what is always true about it?
Two adjacent angles whose non-shared sides form a straight line; they are always supplementary (180°).
What is always true about vertical angles?
They are congruent — the opposite angles formed when two lines cross are equal.
Classify angles by measure
Acute < 90°, right = 90°, obtuse between 90° and 180°, straight = 180°.
Which transversal angle pairs are congruent with parallel lines?
Corresponding, alternate interior, and alternate exterior angles.
Which transversal pair is supplementary?
Same-side (co-interior) interior angles — they add to 180°.
Two lines cross; angles are (3x+10)° and (5x−30)° vertically opposite. Find x and the angles.
3x+10 = 5x−30 → x = 20, so each is 70°; the other two angles are 110°.
Collinear vs. coplanar
Collinear points lie on the same line; coplanar points lie in the same plane.
If one angle formed by a transversal cutting parallel lines is 65°, what are the eight angles?
Four angles measure 65° and four measure 115°.
