2/13/2013
9-4
Perimeter and Area in
the Coordinate Plane
9-4
Perimeter and Area in
the Coordinate Plane
Example 1A: Estimating Areas of Irregular Shapes in
the Coordinate Plane
Example 1A Continued
Estimate the area of the irregular shape.
Method 1: Draw a composite
figure that approximates the
irregular shape and find the
area of the composite figure.
The area is approximately
4 + 5.5 + 2 + 3 + 3 + 4 +
1.5 + 1 + 6 = 30 units2.
Holt Geometry
9-4
Holt Geometry
Perimeter and Area in
the Coordinate Plane
9-4
Perimeter and Area in
the Coordinate Plane
Example 1A Continued
Check It Out! Example 1
Estimate the area of the irregular shape.
Method 2: Count the number
of squares inside the figure,
estimating half squares. Use a
 for a whole square and a
for a half square.
There are approximately 33
whole squares and 9 half
squares, so the area is
about 38 units2.
There are approximately 24
whole squares and 14 half
squares, so the area is about
Holt Geometry
9-4
Holt Geometry
Perimeter and Area in
the Coordinate Plane
Remember!
9-4
Perimeter and Area in
the Coordinate Plane
Example 2: Finding Perimeter and Area in the
Coordinate Plane
Draw and classify the polygon with vertices
E(–1, –1), F(2, –2), G(–1, –4), and H(–4, –3).
Find the perimeter and area of the polygon.
Step 1 Draw the polygon.
Holt Geometry
Holt Geometry
1
2/13/2013
9-4
Perimeter and Area in
the Coordinate Plane
Check It Out! Example 2
Draw and classify the polygon with vertices
H(–3, 4), J(2, 6), K(2, 1), and L(–3, –1). Find
the perimeter and area of the polygon.
9-4
Perimeter and Area in
the Coordinate Plane
Example 3: Finding Areas in the Coordinate Plane by
Subtracting
Find the area of the polygon with vertices
A(–4, 1), B(2, 4), C(4, 1), and D(–2, –2).
Step 1 Draw the polygon.
Draw the polygon and
close it in a rectangle.
Area of rectangle:
A = bh = 8(6)= 48 units2.
Holt Geometry
Holt Geometry
9-4
Perimeter and Area in
the Coordinate Plane
9-4
Perimeter and Area in
the Coordinate Plane
Check It Out! Example 3
Find the area of the polygon with vertices
K(–2, 4), L(6, –2), M(4, –4), and N(–6, –2).
Draw the polygon and
close it in a rectangle.
Area of rectangle:
A = bh = 12(8)= 96 units2.
Holt Geometry
Holt Geometry
2