Final answer:
The steep side of a dune typically has a slope angle equal to the angle of repose for sand.
Step-by-step explanation:
The side of a dune that typically has a slope angle equal to the angle of repose for sand is the steep side of the dune. The angle of repose is the maximum angle at which loose sediments, like sand, will remain stable without sliding or cascading down the slope. In the case of dunes, the side that is facing the direction of the wind or water flow will be steeper and have an angle of repose equal to the angle of repose for sand.