Question

Which biconditional is NOT a good definition?

a. An angle is a right angle if and only if its measure is 90°
b. An angle is acute if and only if its measure is less than 90°
c. Two angles are congruent if and only if its measure are the same.
d. An angle is obtuse if and only if its measure is greater than 180°

Answer 1

the answer is D because and obtuse angle is 91 degrees or more

Answer 2

Option: d is the correct answer.

d. An angle is obtuse if and only if its measure is greater than 180°

Explanation:

Acute angle--

An angle is acute if and only if the measure of the angle is strictly less than 90 degree.

Right angle--

An angle is right angle if and only if the measure of the angle is exactly equal to 90 degree.

Obtuse angle--

An angle is said to be obtuse if and only if the measure of the angle is strictly greater than 90 degree and strictly less than 180 degree.

Congruent angles--

Two angles are said to be congruent if and only if both the angles have the same measure.

Hence, the biconditional which is NOT a good definition is:

Option: d