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Level 69

Perimeter & Area: Geometry


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perimeter
Sum of all sides. Add outside sides together.
Circumference
2πr
Area of Rectangle
A = lw
A =bh
Area of a Parallelogram
A=1/2bh
Area of Triangle
Trapazoid
A=1/2 (b1 + b2)h
Pythagorean Triples
3 4 5
Special Right Angles 30 60 90
Start with smallest leg. Multiply it by 2 where the hypothesis is. Multiply it by radical 3 longest leg.
Special Right Angles 45 45 90
Multiply the leg by radical 2 to get the hypotenuse.
Radii of a circle
1/2 of the diameter.
diameter of a circle
Goes across the circle
If you have (use circumference formula)...
How do I find the circumference with parts of a circle?
Why do I use Pythagorean Theorem?
When you need a side and do not have 30 60 90 or 45 45 90.
What is an irrational number?
A non repeating number. Example radical 2 is 1.732050808
regular polygons
All equal sides, all equal angles.
Center
Each regular polygon has a center because it can be inscribed in a circle.
radius
From center to a point on the circle.
Apothem
The perpendicular distance from the center to a side of a regular polygon.
Special Right Angles
Formed with the radius and the apothem.
.5 (perimeter)(apothem)
Area Regular Polygon