ABCD is a square which means all angle are congruent (90º) and we also know that a square is technically a rhombus, which means the diagonals bisect angles. This means that BD bisects ∠ABC. Knowing ABC is 90º we just simply divide that by 2 to get the answer. For ∠ADC we know what every angle must equal considering they are all congruent and located inside a quadrilateral, and for angle AEB we know that ∠ABE is 45º and ∠BAE is 45º. Since all angles of triangles add up to equal 180º we just set up an equation to find the missing angle.
Where x is m∠AEB:
× + 45 + 45 = 180
x + 45 = 135
x = 90º
