2D Plane Geometric Shapes Exist on a Flat Plane Formulas and Other 2D Shape Information

Area of a Circle

A=πr2

Formula to find Radius

r= d/2

Formula to find Diameter

d=2 * r

Circumference of a Circle

C=2πr or πd

Area of a Triangle

A= 1/2 b * h

Perimeter of a Triangle

P= sum of all sides

Area of a Rectangle

A= L * W

Perimeter of a Rectangle

P= 2L + 2W

Area of a Square

A = S²

Perimeter of a Square

P= 4 * s or S + S + S + S

Area of a Parallelogram

A= b * h

Perimeter of a Parallelogram

P= 2L + 2W

Area of a Trapezoid

A= 1/2 (B2 + B1) * H

Perimeter of a Trapezoid

P= Sum of sides

How to find Height of Trapezoid w/o Area

H= 2 * A/ (B1 + B2)

If given two interior angles of a triangle, you can get the third angle by subtracting the value of the two angles by

180

Scalene/Irregular Triangle

No sides and angles equal same length, but add up to 180

Isosceles Triangle

Two angles and two sides are the same. OTHER side and angle is different

Find Isosceles Triangle Angle by

Subtracting given number by 180

Equilateral Triangle

All sides and angles are equal and all sides add up to 180

Square and Rectangle: Interior angles of 4 sided figure adds up to

360 ; so subtract given angles by 360

Square is a Variation of a

Rectangle, except all of its sides have the same length.

To find Parallelogram Area

Draw a perpendicular line from the base up to the top, becomes height

In what formula must you use the height and not side * height

A= b * h for parallelogram

Top and Bottom are still parallel to each other, but the side aren't parallel to one another

Trapezoid; Top & Bottom are bases, Left & Right are Sides