Flashcards in Geometry Deck (32)

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1

## Bisecting line` `

### Splits something into 2 EQUAL parts`

2

## Be aware that polygons do not have to...

###
...be "regular."

Regular = all sides the same lengt

3

## Sum of interior angles of a triangle

### Add up to 180

4

## Sum of interior angles of a quadrilateral (4 sides)

### Add up to 360

5

## The sum of the interior angles of every pentagon (5 sides)

### Add up to 540

6

## Hexagon - sum of interior angles...

### ...add up to 720

7

## Sum of interior angles of any polygon =

### (n-2)180

8

## Sum of exterior angle and interior angle...

### ...always equals 180

9

## Num of interior angles and exterior angles in every polygon

### Is equal (triangle has 3 interior angles, that add up to 180, and 3 exterior angles)

10

## The sum of the exterior angles of ANY polygon...

### ...is always equal to 360

11

## For triangles - an EXTERIOR angle of a triangle is always equal to....

### ...the SUM Of the NON-ADJACENT interior angles.

12

## Never assume...

### ...that the lines are parallel, angle is right, shape is a square, etc. (Unless the exam explicitly states otherwise)

13

## Tricky problem with lines and angles...

###
1. Draw the diagram

2. Look for relationships you know

3. Don't be afraid to "tune out" lines temporarily

4. If you can find >1 equation , COMBINE equations using subtraction or elimination

5. Look back at the diagram to see if your solutions make sense with the general shape

14

## 180-x trick

### Label ALL of the interior (or exterior) angles of the polygon, using 180-x

15

## Isosceles

###
2 angles of = measure, 2 sides of = measure.

NOTE - an equilateral is just a SPECIAL type of isosceles.

16

## Pythagorean triples

###
3-4-5 (6-8-10; 9-12-15; 12-16-20; 15-20-25)

5-12-13 (10-24-26)

8-15-17

7-24-25

17

## 45-45-90 triangles [isosceles right triangle]

### x:x:x(sq.rt of 2)

18

## 45-45-90 Short-Cut

### CUT the hypothenuse in HALF and MULTIPLY the result by sq. root of 2

19

## Every equilateral triangle

### Is composed of TWO 30-60-90 triangles

20

## Perimeter and triangle inequality theorem

###
Sum of any two sides of any triangle must be greater than the third side. Conversely, the difference of any two sides must be less than the third.

LESS THAN THE SUM, BUT GREATER THAN THE DIFFERENCE

21

## Parallelogram - adjacent angles

### Always add up to 180

22

## Diagonals of a parallelogram...

### ...bisect one another and split the shape into two equilateral triangles

23

## Area of a parallelogram

### Is equal to BASE times HEIGHT

24

## Area of a trapezoid

### Average of bases x height

25

## Units in a surface area question...

### ...should be squared

26

## Volume of a rectangular solid

### Length x Width x Height

27

## Units when calculating volumen...

### Should be cubed

28

## How to determine the interior diagonal of a rectangular slid?

###
The Diagonal of a Rectangular Solid = square root of (lˆ2 + wˆ2 + hˆ2)

29

## Diagonal of a Cube

###
Diagonal of a Cube = s (square root of 3)

S = side length

30