What is the biconditional statement of the following conditional statement? "If the product of the slopes of two lines is −1, then the lines are perpendicular." If the lines are perpendicular, then the product of the slopes of two lines is −1. The product of the slopes of two lines is −1 if and only if the lines are perpendicular. If the product of the slopes of two lines is not −1, then the lines are not perpendicular. If the two lines are not perpendicular, then the product of the slopes of two lines is not −1.