Answer:
Two angles are said to be vertical angles if and only if their sides form two pairs of opposite rays.
Explanation:
A biconditional statement is one that must fulfill the two conditions of the statement for it to be true. The two required conditions in the statement are always connected by if and only if.
The required statement is: Two angles are said to be vertical angles if and only if their sides form two pairs of opposite rays
Vertical angles are equal and opposite. Therefore for the biconditional statement to be true, the angles should be vertical and their sides must form two pairs of opposite rays.