If two lines intersect, then the vertical angles formed must choices are: both acute angles. both equal in measure. complementary angles

The correct answer is: both equal in measure :)

If two lines intersect, then the vertical angles formed must be both equal in measure. The correct option among all the options that are given in the question is the second option or the penultimate option. I hope that this is the answer that has actually come to your great help.

Because three (non-colinear) points are needed to determine a unique plane in Euclidean geometry. Given two points, there is exactly one line that can contain them, but infinitely many planes can contain that line. Three points, as long as they don't all lie on the same line, do determine a unique plane.