1. Intro to Geometry in 2D
These are your notes for Area of 2 Dimensional figures…Write & Draw EVERY detail as if I was at the front of class. Write down any questions you may have, ask the substitute, or a neighbor! 

2. HAVE YOU NOT GOT OFF THIS SLIDE YET?
COME ON! GET MOVING GUYS!
By:Jeffrey McAven

3. Lets look at 2 Dimensional Shapes and their Formulas
Triangles (3 sides)
Quadrilaterals (4 sides)
Polygons-3 or more sides, must be closed, no curved or overlapping sides

4. Polygons- Any closed shape made up of straight lines.
We have already talked about Triangles and Quadrilaterals, lets look at some more common polygons.
Pentagon (5 sides)
Hexagon (6 sides)
Heptagon (7 sides)
Octagon (8 sides)
Nonagon (9 sides)
Decagon (10 sides)
You do not need to know the formulas for these but should be able to recognize them.

5. Perimeter
To find the perimeter of any polygon all you need to do is add the sides.

6. Perimeter

7. Quadrilaterals
A Quadrilateral is any four sided figure. Lets look at the most common.
Square – All Sides and Angles same A=s2 or A=base(height)
Rectangle – All Angles are the same and parallel sides are the same measure A=base(height)

8. Squares and Rectangles
Area of Rectangle: A = bh
Area of Square: A = s² s
A = s² b h
A = bh
Example:
Example: 12 5 6
A = 6² = 36 sq. units
A = 12 x 5 = 60 sq. units

9. Quadrilaterals Parallelogram – Parallel side are the same A=bh
Rhombus A=bh
Trapezoid

10. Parallelograms & Rhombus
Area of Parallelogram: A = b(h)
Area of Rhombus: A = b(h)
Example: h b
Example: 6 9
A = 9 x 6 = 54 sq. units

11. Trapezoids Or
The height (h) is the distance between the two bases b1 & b2, perpendicular to each base h b1 b2

12. Triangles
A Triangle is a three sided figure. All triangles have the same Area formula or

13. Triangles Right Triangle – Has one angle 90○
Acute Triangle – Every angle is less than 90○
Obtuse Triangle –Has one angle more than 90○

14. Triangles
Equilateral Triangle – All angles and sides are the same measure
Isosceles Triangle – Two sides are the same and two angles are the same
Scalene Triangle – All sides and angles are different

15. Triangles Or
h is the distance from a vertex of the triangle perpendicular to the opposite side. h b

16. Circles
Circumference of a circle is the distance around the outside of the circle. The formula is C=2πr or C= πd
Area formula for a circle is A= πr2

17. Area of a Circle
Area formula for a circle is A= πr2

18. Circumference of a Circle
Circumference formula for a circle is or

19. Area of Composite Figures
The area of a composite figure is the sum of all of its non-overlapping parts. 8 10 12 4 14
A = ½(8)(10)
A= 40
A = (12)(10)
A= 120
A = (4)(8)
A=32
A = (14)(8)
A=112
Area = = 304 sq. units

20. Answers: 140cm2 56cm2 180cm2 168cm2 132cm2 240cm2 330cm2 72cm2 225cm29 8 10
14cm
12cm
18cm
9cm
16cm
12cm
20cm 12 11
8cm
14cm 13
25cm
15cm
14cm
15cm
12cm
16cm
12cm

21. Try these on your own!!! 2 3 1 9cm 12cm 13cm 4 8cm 15cm 4cm 15cm 9cm 67
9cm
12cm
11cm
12cm
15cm
14cm
40cm
12cm 9 8 10
14cm
8cm
8cm
20cm
18cm
8cm
40cm 12 11
24cm
18cm 13
35cm
25cm
14cm
15cm
12cm
36cm
22cm