Question

Select the counterexample to this conjecture:

A pair of supplementary angles includes one obtuse angle.
A.90º + 90º = 180º B.120º + 60º = 180º C.100º + 80º = 180º D.110º + 70º = 180º

Answer 1

The counterexample to the conjecture that a pair of supplementary angles includes one obtuse angle is option A, 90º + 90º = 180º.

Step-by-step explanation:

The counterexample to the conjecture that a pair of supplementary angles includes one obtuse angle is option A, 90º + 90º = 180º.

In this case, both angles are right angles and not obtuse angles.

To be an obtuse angle, one angle in the pair must be greater than 90 degrees.

Answer 2

the answer is .90º + 90º = 180º, .90º is not an obtuse angle