Lessons 1, 2, 3 in Grade 7 Mathematics.ppt
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The document discusses the sum of the interior angles of polygons, providing formulas for calculating these sums based on the number of sides. It includes examples demonstrating how to find interior angles and work with equations to solve for unknown values. Additionally, it briefly mentions the sum of exterior angles in a convex polygon.
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Lessons 1, 2, 3 in Grade 7 Mathematics.ppt
- 5. If all the s in a Δ add up to 180o. Then what about the s in a quadrilateral and pentagon? 3 * 180 = 540o How about a hexagon? 4 * 180 = 720o 2 * 180 = 3600
- 6. # of sides # of triangles Sum of measures of interior angles 3 1 1(180)=180 4 2 2(180)=360 5 3 3(180)=540 6 4 4(180)=720 n n-2 (n-2) • 180
- 7. If a convex polygon has n sides, then the sum of the measure of the interior angles is (n – 2)(180°)
- 8. If a regular convex polygon has n sides, then the measure of one of the interior angles is n n 180 ) 2 (
- 9. Ex. 1 Use a regular 15-gon to answer the questions. A)Find the sum of the measures of the interior angles. B)Find the measure of ONE interior angle 2340° 156°
- 10. Ex: 2 Find the value of x in the polygon 130 126 143 100 117 x 126 + 130 + 117 + 143 + 100 + x = 720 616 + x = 720 x = 104
- 11. Ex: 3 The measure of each interior angle is 150°, how many sides does the regular polygon have? n n 180 ) 2 ( One interior angle 150 180 ) 2 ( n n n n 150 180 ) 2 ( n n 150 360 180 360 30 n 12 n A regular dodecagon
- 12. Two more important terms Exterior Angles Interior Angles
- 14. The sum of the measures of the exterior angles of a convex polygon, one at each vertex, is 180°. 1 2 3 4 5 1 3 2 1 3 2 4
- 20. Look on the bottom of the Worksheet