question still somewhat vague?
however ...
in euclidean geometry
the sum of all angles within a triangle add to 180 degrees
if the triangle is a right angled triangle then one angle is 90 degrees
so the sum of the remaining two angles must add to 90 degrees (180-90=90)
if the triangle is a right angles isosceles triangle the the two remaining angles are equal and so each 45 degrees (90/2=45)
in non-euclidean geometry other sum of angles rules apply
