Regular decagon ABCDEFGHIJ rotates 360 degrees counterclockwise about it's center. At which angle of rotation does A' (the image of A) coincide with D?

Question

happyfeet8040 · Answer

We need to find what angle the vector A makes with the the vector D.

the central angle subtended by each side is (360/10)

the angle made by A' with vector D is 180-7*(360/10)

since the rotation is counterclockwise the angle you are looking for is 360-(180-7*(360/10))