Chapter 11

Area of a regular polygon

Area = ½ (apothem)(perimeter)

Area of a circle

πr²

Circumference of cirlce

π(d)

Sector definition

A region bounded by 2 radii and an arc of the circle

If m of arc AB = x, arc length of AB is

(x/360)πd

Area of sector

(x/360)πr²

The ratio of the areas of 2 triangles with equal heights

Ratio of the bases

The ratio of the areas of 2 triangles with equal bases

Ratio of the heights

The ratio of the areas of 2 similar triangles

Scale factor squared

Thm: If the scale factor of 2 similar figures is a:b, then

1. The ratio of the perimeters is a:b

2. The ratio of the areas is a²:b²

Geometric probablity principle 1 (segment)

If a point on segment AB is picked at random then the probablity that p is on AC is:

Length of AC/Length of AB

Geometric probability principle 2 (space)

If a point in region S is picked at random, then the probability that p is in region R is:

Area of R/Area of S

Area of a parallelogram

Base times Height

Area of Triangle

½ base times height

Area of a trapezoid

½ height (base1+base2)

Area of Rhombi and kites

½ (diagonal 1) (diagonal2)