__Section 11.1 Areas of Parallelograms__

**Area of a Parallelogram**

**A **(area) =** b
**(base) *** h **(height)**
A = bh**

The sum of all sides of the polygon (the distance around the polygon)

**P = (add all sides)**

**Examples:**

Find the shaded area of the figure

__Section 11.2 Areas of Triangles, Trapezoids, and Rhombi__

__Area of a Triangle__

**A **(area)
=** ****1/2 ***
**b**** **(base)
*** h
**(height)

**A = 1/2 bh or
A = bh/2**

__Area of a Trapezoid__

**A **(area)
=** ****1/2 ***
**h **(height)*** (b****1
+ b2) **

**A = 1/2 h (b1
+ b2)**

__Area of a Rhombus, Kite, Square
__(Or ANY Quadrilateral with perpendicular diagonals)

**A **
=** ****1/2 **
*
**d1
*
****d****2
d1 **and**
****d****2
**are the diagonals

**Postulate 11.1**:
Congruent figures have equal areas

**Examples:**

__Section 11.3 Areas of Regular Polygons and Circles__

**Regular Polygon**: a
polygon with congruent sides and congruent angles

**Parts of a Regular
Polygon**

**Center of a
Regular Polygon**—the center of the circumscribed circle.

**Radius of a
Regular Polygon**—the radius of the circumscribed circle.

**Apothem of a
Regular Polygon**—the distance from the center to the midpoint of any side of the polygon.

**Central Angle
of a Regular Polygon**—an angle whose vertex is the center and whose sides
contain two consecutive vertices of the polygon.

**To find the
area of a Regular Polygon**:

**
**Find each of the following values:

Apothem (a)

Base (b)

Side (s)

Perimeter (P)

Area (A)

**Area of a Circle**

**Examples:**

__Section 11.4 Areas of Irregular Figures__

**Examples of Irregular Polygons:**

__Section 11.5 Geometric Probability__

**Sector: portion of a
circle bounded by a central angle and its intercepted arc**

**Area of a Sector**

N is the measure of the central angle (or the intercepted arc)

r is the radius of the circle

**Probability**: desired
outcome (area)/ possible outcome (area)

The probability of an event = successful possible area / total possible area

The probability of an event = successful possible length / total possible length

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