Determine whether the conditional and its converse are both true. if both are true, combine them as a biconditional. if either is false, provide a counterexample. if an angle is a right angle, its measure is 90. if an angle measure is 90, the angle is a right angle. both statements are true. an angle is a right angle if and only if its measure is 90. both statements are true. the measure of an angle is 90 if and only if it is not a right angle. one statement is false. if an angle is a right angle, its measure may be 180. one statement is false. if an angle measure is 90, the angle may be an obtuse angle.