5.) Geometry & Measures Flashcards
What do (internal) angles in a triangle and a quadrilateral add up to?
- Angles in a triangle add up to 180°
- Angles in a quadrilateral add up to 360°
What do alternate, allied and corresponding angles (of parallel lines) look like and what are their rules?
- Alternate angles are equal (Z shape)
- Allied angles add up to 180° (C or U shape)
- Corresponding angles are the same (F shape)
What do the sum exterior and interior angles of any polygon make up?
- Sum of exterior angles is always 360°
- Sum of the interior angles = (number of sides – 2) * 180°
For regular polygons, how do you find each individual interior and exterior angle?
- Exterior angle = 360° ÷ number of sides
- Interior angle is just 180° - the exterior angle
(Rule of circle geometry) involving the angle of a tangent and radius:
- They always meet at 90°
(Rule of circle geometry) What do 2 radii form?
- An isosceles triangle
(Rule of circle geometry) What is the angle of a point on the circumference drawn out from two ends of a diameter, aka the angle of a semicircle?
- 90°
(Rule of circle geometry) The one about perpendicular bisector and chord? Also what do those two phrases mean?
- The perpendicular bisector of a chord always passes through the centre of a circle
- A chord is any straight line through a circle
- A perpendicular bisector cuts a line at 90°
(Rule of circle geometry) How do the angles at the centre and at the circumference relate?
- The angle at the centre of the circle is always the angle at the circumference
(Rule of circle geometry) What can you say about angles in the same segment?
- They are equal
- (2 angles drawn from the same chord)
(Rule of circle geometry) What can you say about opposite angles in a cyclic quadrilateral? And what is a cyclic quadrilateral
- A cyclic quadrilateral is inside a circle where all four points touch the circumference
- 2 opposite angles in a cyclic quadrilateral always add up to 180°
(Rule of circle geometry) What can you say about 2 tangents from the same point?
- They are the same length
- As they are both the hypotenuse of 2 congruent right-angled triangles
(Rule of circle geometry) What is the alternate segment theorem?
- The angle between a tangent & chord is the same as the angle in the opposite segment
Four ways of proving a pair of triangles being congruent?
- SSS: 3 sides are the same length
- AAS: 2 sides and a corresponding angle match up
- SAS: 2 sides and the angle in between them match up
- RHS: The hypotenuse and another side of a right angle match up
Difference between “similar” and congruent?
- Two congruent shapes are the same shape and size
- Two similar shapes are the same shape but different size