# Geometry Flashcards

Area of a triangle

(B x H) / 2 = Area

Area of a rectangle

L x H = Area

Area of a trapezoid

((Base1 + Base2) / 2) x H = Area

Area of a parallelogram

B x H = Area

Area of a rhombus

(Diagonal x Diagonal) / 2 = Area

Volume of a rectangular solid

L x W x H = Area

Formula for sum of interior angles of a polygon

(n - 2) * 180

Three common types of right triangles

1) 3 - 4 - 5 (6,8,9) (9,12,15) (12,16,20)

2) 5 - 12 - 13 (10,24,26)

3) 8 - 15 - 17

Ratio of sides for isosceles triangles

45 - 45 - 90

1 : 1 : √2

x : x : √x

Ratio of sides for equilateral triangles

30 - 60 - 90

1 : √3 : 2

x : x√3 : 2x

Formula for diagonal of a square

d = s√2

Formula for diagonal of a cube

d = s√3

Ratio of similar triangle side lengths to area ratios

Length - a : b

Area - a² : b²

Formula for area of an equilateral triangle

(S²√3) / 4 = Area

Circumference of a circle

C = 2πr or C = dπ