Question

multiple similarity transformations are performed on a triangle. which elements must be preserved?
orientation
side length
angle measure
overall size

Explanation:

Similarity transformations (such as dilation, rotation, translation, reflection) change orientation (in case of reflection), side - length (in case of dilation), and overall size (in case of dilation). But by the definition of similar triangles, the ratio of corresponding sides is equal (so angles, which are related to the shape and determined by the ratios of sides, are preserved).

Answer:

angle measure