One interior angle of a triangle is 45°, and the other two angles are congruent. Choose the equation that could be used to determine the degree measure of one of the congruent angles.
a) x + 45 = 180
b) x − 45 = 90
c) 2x + 45 = 180
d) 2x − 45 = 90
The sum of the interior angles of a triangle is always 180°. Since one of the angles is 45° and the other two angles are congruent, we can represent the degree measure of one of the congruent angles as x. Therefore, the equation that can be used to determine the degree measure of one of the congruent angles is:
2x + 45 = 180.
Thus, the correct answer is (c) 2x + 45 = 180.