Determine if the biconditional is true. If false, give a counterexample.
An angle is a right angle if and only if it is not obtuse.

false; m∠1 = 120°, ∠1 is not a right angle

false; m∠1 = 70°, ∠1 is not a right angle

false; m∠1 = 90°, ∠1 is not an obtuse angle

true