sec 2 Flashcards
geom (70 cards)
What is a straight line?
A line that extends infinitely in both directions.
Symbol: ←———→
Example: A horizon line
What is a line segment?
A part of a line with two endpoints.
Symbol: A———B
Example: The side of a triangle
What is a ray?
A part of a line with one endpoint that extends
infinitely in one direction.
Symbol: A———→
Example: A light beam from a torch
What are parallel lines?
Lines in the same plane that never meet
and are always the same distance apart.
Symbol: ∥
Example: Railway tracks
What are perpendicular lines?
Lines that meet at a right angle (90°).
Symbol: ⊥
Example: The corner of a page
What is an acute angle?
An angle that measures less than 90°.
Example: 45° is an acute angle.
Visual: ∠ (with a small opening)
What is a right angle?
An angle that measures exactly 90°.
Symbol: ⊥ or ∟
Example: The corner of a square
What is an obtuse angle?
An angle that measures more than 90° but less than 180°.
Example: 120° is an obtuse angle.
Visual: ∠ (with a wide opening)
What is a straight angle?
An angle that measures exactly 180°.
Example: A straight line forms a straight angle.
Visual: ——
What is a reflex angle?
An angle that measures more than 180° but less than 360°.
Example: 270° is a reflex angle.
Visual: The larger part of a circle when a smaller angle is formed
What are complementary angles?
Two angles whose sum equals 90°.
Example: 30° and 60° are complementary angles
because 30° + 60° = 90°
What are supplementary angles?
Two angles whose sum equals 180°.
Example: 45° and 135° are supplementary angles
because 45° + 135° = 180°
What are vertically opposite angles?
Pairs of opposite angles formed when two straight
lines intersect. Vertically opposite angles are equal.
Visual: When lines form an X, the opposite
angles are equal
What is the sum of angles on a straight line?
180°
Example: If one angle is 65°, the other angle
on the same straight line is 115° (180° - 65° = 115°)
What is the sum of angles around a point?
360°
Example: If three angles around a point are 90°, 120°,
and x°, then x = 150° (360° - 90° - 120° = 150°)
What are corresponding angles?
When a transversal crosses two parallel lines,
corresponding angles are in the same position
relative to each parallel line and the transversal.
Corresponding angles are EQUAL.
Visual: Use the F-pattern to identify them
What are alternate angles?
When a transversal crosses two parallel lines,
alternate angles are on opposite sides of the
transversal and between the parallel lines.
Alternate angles are EQUAL.
Visual: Use the Z-pattern to identify them
What are co-interior angles?
When a transversal crosses two parallel lines,
co-interior angles are on the same side of the
transversal and between the parallel lines.
Co-interior angles SUM TO 180°.
Visual: Use the C-pattern to identify them
What is an equilateral triangle?
A triangle with all three sides equal in length
and all three angles equal (60° each).
Properties:
- All sides equal
- All angles equal (60°)
- Three lines of symmetry
What is an isosceles triangle?
A triangle with two sides equal in length
and two angles equal.
Properties:
- Two sides equal
- Two angles equal (the base angles)
- One line of symmetry
What is a scalene triangle?
A triangle with no sides equal in length
and no angles equal.
Properties:
- All sides different lengths
- All angles different measures
- No lines of symmetry
What is an acute triangle?
A triangle with all three angles measuring less than 90°.
Example: A triangle with angles 60°, 60°, and 60°
What is a right-angled triangle?
A triangle with one angle measuring exactly 90°.
Properties:
- Pythagoras’ theorem applies
- The longest side (opposite the right angle) is the hypotenuse
Example: A triangle with angles 90°, 45°, and 45°
What is an obtuse triangle?
A triangle with one angle measuring more than 90°.
Example: A triangle with angles 30°, 60°, and 90°