1. The problem statement, all variables and given/known data How does angle DAE equal a/2 + 90 degrees (a refers to the angle at vector A)? Please refer to the picture attached. Triangles ACE and ABD are isosceles. Side h bisects triangle ABC. Segment ED equals the perimeter of triangle ABC 2. Relevant equations 3. The attempt at a solution According to the solution, Angle DAE equals a/2 + 90 degrees. a refers to the angle at Vector A of triangle ABC. I realize the acute angles of AEC and ABD are the same in their respective triangles. Altitude h intersecting at CB makes it 90 degrees on either side, but says nothing further of the angle ( angle a) at vector A.