Answer:
From the sum of angles on a straight line, given that the rotation of each triangle attached to the sides of the octagon is 45° as they move round the perimeter of the octagon, the angle a which is supplementary to the angle turned by the triangles must be 135 degrees
Step-by-step explanation:
Given that the triangles are eight in number we have;
1) (To simplify), we consider the five triangles on the left portion of the figure, starting from the bottom-most triangle which is inverted upside down
2) We note that to get to the topmost triangle which is upright , we count four triangles, which is four turns
3) Since the bottom-most triangle is upside down and the topmost triangle, we have made a turn of 180° to go from bottom to top
4) Therefore, the angle of each of the four turns we turned = 180°/4 = 45°
5) When we extend the side of the octagon that bounds the bottom-most triangle to the left to form a straight line, we see the 45° which is the angle formed between the base of the next triangle on the left and the straight line we drew
6) Knowing that the angles on a straight line sum to 180° we get interior angle in between the base of the next triangle on the left referred to above and the base of the bottom-most triangle as 180° - 45° = 135°.
