Name ________________________________________ Date __________________ Class __________________ 10-4 Reteach Perimeter and Area in the Coordinate Plane One way to estimate the area of irregular shapes in the coordinate plane is to count the squares on the grid. You can estimate the number of whole squares and the number of half squares and then add. The polygon with vertices A( 3, 1), B( 3, 3), C(2, 3), and D(4, 1) is drawn in the coordinate plane. The figure is a trapezoid. Use the Distance Formula to find the length of CD . CD 4 2 2 1 3 perimeter of ABCD: P 2 AB 20 2 5 BC CD 4 5 2 5 DA 7 20.5 units area of ABCD: A 1 b1 2 b2 h 1 5 2 7 4 24 units2 Estimate the area of each irregular shape. 1. _________________________________________ 2. ________________________________________ Draw and classify each polygon with the given vertices. Find the perimeter and area of each polygon. 3. F( 2, 3), G( 2, 3), H(2, 0) 4. Q( 4, 0), R( 2, 4), S(2, 2), T(0, 2) _________________________________________ ________________________________________ _________________________________________ ________________________________________ Original content Copyright © by Holt McDougal. Additions and changes to the original content are the responsibility of the instructor. Holt McDougal Geometry Name ________________________________________ Date __________________ Class __________________ Reteach Perimeter and Area in the Coordinate Plane continued When a figure in a coordinate plane does not have an area formula, another method can be used to find its area. Find the area of the polygon with vertices N( 4, 1), P( 1, 3), Q(4, 3), and R(2, 2). Step 1 Draw the polygon and enclose it in a rectangle. Step 2 Find the area of the rectangle and the areas of the parts of the rectangle that are not included in the figure. rectangle: A Step 3 bh 8•5 40 units2 a: A 1 bh 2 1 3 4 2 6 units2 b: A 1 bh 2 1 2 5 2 5 units2 c: A 1 bh 2 1 6 1 2 3 units2 Subtract to find the area of polygon NPQR. A area of rectangle 40 6 26 units 5 area of parts not included in figure 3 2 Find the area of each polygon with the given vertices. 5. 6. _________________________________________ 7. A( 1, 1), B( 2, 3), C(2, 4), D(4, 1) _________________________________________ ________________________________________ 8. H(3, 7), J(7, 2), K(4, 0), L(1, 1) ________________________________________ Original content Copyright © by Holt McDougal. Additions and changes to the original content are the responsibility of the instructor. Holt McDougal Geometry Name ________________________________________ Date __________________ Class __________________ 3.P 19.8 units; A Reteach 22 units2 1. A 30 units2 35.5 units2 2. A 3. 4. P 18.3 units; A 8 units2 triangle; P 16 units; A square; P 17.9 units; A 12 units2 4. 5. m W 117°; m X m Z 45° 45°; m Y 153°; 20 units2 5. A 29 units2 6. A 20.5 units2 7. A 18 units2 8. A 21.5 units2 Challenge 1. A 0.063 units2 2. about 32 3. Answers will vary: 2 4. about 16 6. m F 47°; m G m I 55° 105°; m H 153°; 5. Answers will vary: 1 6. Answers will vary: 0 Problem Solving 1. P 22.8 units; A 28 units2 2. P 12.1 units; A 4 units2 3. A 31.5 units2 4. Possible answer: A 36 m2 5. C 6. F 7. D Original content Copyright © by Holt McDougal. Additions and changes to the original content are the responsibility of the instructor. Holt McDougal Geometry

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