Statement in step 8 is the proof that <ABD and <EBC are complementary angles.
What are a complementary angles?
An angle in mathematics refers to an arc that joins two points. For angles to be formed there should be two points, the starting point and the ending point. In some cases the starting point coincides with the ending point, in this case the angle formed is 360 degrees which is equivalent to a circle. We can hence say that angle in a circle is 360 degrees
When angles are formed by two points in the same straight line or say two colinear points the angle formed here is 180 degree. Hence we say angles in a straight line is 180 degrees. In a case where a line intersects the straight line, the intersecting line bisects the the angle in a straight line. The sum of the two angles formed is 180 degrees. Such angles are said to be supplementary angles.
Assuming the bisector of the straight line in a perpendicular bisector, here the angle 180 is divided into two equal parts then each angle is 90 degrees.
When angle 90 degrees is bisected two different angles are formed. The sum of these two angles are known as complementary angles.
Hence angle <ABD and <EBC are complementary angles formed from bisecting angle <DBC which is 90 degrees or a right angle triangle
Read more on complementary angles here: https://brainly.com/question/98924
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