Answer :
The inner edge of the arch in the diagram is half of a regular 18-gon. This means that the angle at the center of each trapezoid is equal to the central angle of a regular 18-gon, which can be calculated as 360 degrees divided by 18, or 20 degrees.
Since each trapezoid is isosceles, it has two congruent base angles. To find the measure of each base angle, we can subtract the central angle from 180 degrees and divide the result by 2. So, (180 degrees - 20 degrees) / 2 = 80 degrees.
Therefore, each base angle of the isosceles trapezoid is 80 degrees. Since the trapezoids are congruent, all nine trapezoids in the arch have the same angle measurements.
To draw a nine-stone arch like the one shown, you can start by drawing a straight line segment for the base of the arch. Then, draw a line segment perpendicular to the base at each endpoint. Connect the endpoints of these perpendicular line segments to form the sides of the trapezoids. Finally, draw the upper base of each trapezoid parallel to the lower base, ensuring that the distance between the upper and lower bases remains consistent.
By following these steps, you will accurately draw a nine-stone arch where each of the trapezoids is congruent.
Learn more about angle from the given link:
https://brainly.com/question/25716982
#SPJ11
