4. Given that α−l−β is a right dihedral angle, A∈α,B∈β,A,B are not on l, and let the angles formed by AB with α and β be θ1 and θ2, respectively, then the range of θ1+θ2 is -
Official solution
(0,2π);
Source: NuminaMath-1.5,
licensed Apache-2.0.
Statement and solution reproduced as published; topic, difficulty and ordering added
by this site.