1. Surface area and Volume
Ch 11-13
Sol: G.10,12,13,14

2. Polygon Area Formulas Parallelogram: 𝐴=𝑏ℎ Triangle: 𝐴= 1 2 𝑏ℎ
Trapezoid: 𝐴= 1 2 ℎ( 𝑏 1 + 𝑏 2 )
Rhombus: 𝐴= 1 2 ( 𝑑 1 𝑑 2 )
Regular Polygons 𝐴= 1 2 (𝑎)(𝑝)

3. Area of a Parallelogram: If a parallelogram has an area of A square units, a base of b units, and a height of h units, then A = bh. Example: Find the area of parallelogram STAR.
Parallelogram: 𝐴=𝑏ℎ
In this case, we need to find h.
Since we know that we have a right angle, and that angle T is 450, we can use trigonometry to find h.
Side h is opposite the given angle, and the hypotenuse is given as 9.
sin 45 = ℎ 9 ;9 sin 45 =ℎ
ℎ=6.364
Now that we have h, the formula is easy.
𝐴=𝑏ℎ
𝐴=20(6.364) 𝐴=

4. Area of a Triangle: If a triangle has an area of A square units, a base of b units, and a corresponding height of h units, then A = ½bh. Example: Find the area of THE.
Triangle: 𝐴= 1 2 𝑏ℎ
𝐴= 1 2 (13)(4.5)
𝐴= 1 2 (58.5)
𝐴=29.25

5. Area of a Trapezoid: If a trapezoid has an area of A square units, bases of b1 units and b2 units, and height of h units, then A = ½h(b1 + b2). Example: Find the area of trapezoid TRAP.
Trapezoid: 𝐴= 1 2 ℎ( 𝑏 1 + 𝑏 2 )
𝐴= 1 2 (7)(38+44)
𝐴= 1 2 (7)(82)
𝐴= 1 2 (574)
𝐴=287

6. Area of a Rhombus: If a rhombus has an area of A square units and diagonals of d1 and d2 units, then A = ½d1d2. Example: Find the area of rhombus SANE, if AE = 12 and SN = 8.
Rhombus: 𝐴= 1 2 ( 𝑑 1 𝑑 2 )
𝐴= 1 2 (12∗8)
𝐴= 1 2 (96)
𝐴=48

7. Areas of Regular Polygons
If a regular polygon has an area of A square units, a perimeter of P units, and an apothem of a units, then A = ½ (a)(p).
The apothem is the distance from the center of a regular polygon to the midpoint of a side.
(For a circle it is the distance from the center to the midpoint of a chord.)
Perimeter = 8 6 =48
apothem = 4 3
Area =
1 2 ( ) 8
Lesson 9-1: Area of 2-D Shapes

8. IXL Assignments S2, S3, and S4
Must achieve a Smart Score of at least 80.
Begin work on these in class TODAY (now!!)
These are due by the end of the day Friday.