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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