text: state the truth value of the conditional, converse, and biconditional.? a) two lines form congruent adjacent angles if and only if the two lines are perpendicualar. b) two angles are congruent iff the angles are right angles. iff(if and only if) explain how you got the answer. a) true.  perpendicular lines form 90 degree angles. if they were not perpendicular, then the angles would not be 90.  the two angles have to add up to 180.   if the lines are perpendicular, then both angles are 90. 90 + 90 = 180 if the lines are not perpendicular, then one angle has to be less than 90 and the other will be greater than 90. since one is less than 90 and the other is greater than 90, the angles can't be congruent because they are not equal.  b) false.  two angles are congruent if they have the same angle measure. if measure of angle a is 65, and measure of angle b is also 65, then angle a is congruent to angle b.  the angle measures do not have to be 90.