100 points
i need
make a long answer and short answer

a regular decagon is a polygon with ten sides of equal length. use complete sentences to design a strategy to determine the sum of the interior angles of a regular decagon. in your final answer, include the sum and all of your calculations.

also make it clear ; )

Sum of the interior angles = 1440 degrees.

Step-by-step explanation:

There are a total of 10 interior angles in the decagon. Now for all polygons the sum of all the exterior angles is 360 degrees.  There are 10 exterior angles in the decagon  and, since it is regular, each of them = 360/10 = 36 degrees. Each interior angle therefore  measures 180 - 36 degrees and the sum of the interior angles is this value times ten.

360 / 10 = 36.

180 - 36 = 144.

10 * 144 = 1440 degrees.

the answer is 1440

Step-by-step explanation:

I needed points too :P

1. supplementary angles

2. acd and bcd

step-by-step explanation: