Sum of Interior Angles

                         Lesson 1


                                                Problem:  What is the sum of the interior angles of a Decagon?  


                                                Solution   Formula:  Sum of Interior Angles = 180(n-2)  

                                                Step 1:        


                                                Solution   The decagon has 10 sides.  So n = 10. 

                                                Step 2:        


                                                Solution   180(10-2) = 180(8) = 1440.

                                                Step 3: 


                                                Solution   Answer is: 1440

                                                Step 4:                                        


                                                Try two practice problems:


                                                                   Do the following:



What is a polygon called if the sum of its interior angles equals 540?


How many degrees are there in the sum of the interior angles of twenty sided polygon?











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