see the attached figure to better understand the problem
we know that
1) If angle 1 and angle 2 are complementary angles
then
m∠1+m∠2=[tex]90\°[/tex] ------> equation A
2) If angle 1 and angle 2 are congruent angles
then
m∠1=m∠2 ------> equation B
Substitute equation B in equation A
m∠1+(m∠1)=[tex]90\°[/tex]
2m∠1=[tex]90\°[/tex]
m∠1=[tex]45\°[/tex]
therefore
the answer is
[tex]45\°[/tex]
