Ch. 11 First Quiz Flashcards
Circumference
C=πd or C= 2πr
Only multiply π when…
- Instructed to do so
- In a real-life problem
- If the author has already done it
How to find the arc length in a circle
Central angle/360 * circumference
How to find the perimeter of polygons
Circumference of the pieces π + straight pieces
Only need sides that are actually on the outside
How to convert angle measures to radians
180/π = angle measure/x (radians)
Solve for x
How to convert radians to angle measures
Replace π with 180 degrees and solve
Area of a circle
πr²
How to find the area of a section of a circle
A= x(angle of the section)/360 * πr²
Population Density
Number of people/area of land (use π)
How to solve a Shade
Everything in a circle minus what’s included
How to find the central angle of a polygon
360/number of sides
What is the apothem?
The perpendicular line from the center of the polygon to a side
How to find the area of a regular polygon
A= 1/2 (apothem) (base) (# of sides)
Steps to find Area of a polygon
1] 360/# of sides (find central angle)
2] Drop apothem (splits angle and base)
3] Plug in known values and solve with formula
Area of a rhombus/kite
1/2 (d1 * d2)
Difference between arc measure and arc length
AM- Degrees
AL- Feet, meters, etc.
How to find the radius when you have the circumference
Divide the circumference by 2π
How to find a perimeter with straight pieces and semi-circles in a polygon
360-known angle = New angle
New angle/360 * circum.
Multiply the top by the number of curved pieces
Add perimeter of straight pieces
Finding the area with a fraction
Square both parts
π goes on top
How to find the area of a few triangles in a circle
Pie
Turn shaded into a fraction
Shaded/Total triangles * Total area
Find arc measure in a circle
Arc measure/360 * Area of circle
How to find the area of an equilateral triangle
A= √3/4 * side²
Radius on a regular polygon
The line from the center to the corner
Find area of a square with diagonal
A = 1/2d²
