The measure of one interior angle of a triangle is 45°. What can you conclude about the other two interior angles of the triangle?

One of the other angles must be a right angle.
The sum of the measures of the other two angles is 135°.
The other two angles must be acute angles.
One of the other angles must have a measure greater than 90°.

1 answer

In a triangle, the sum of the measures of the interior angles is always 180°. Given that one interior angle is 45°, we can determine the sum of the measures of the other two angles as follows:

\[ 180° - 45° = 135° \]

This means that the sum of the measures of the other two angles is 135°. Now, let's analyze the statements one by one:

  1. One of the other angles must be a right angle. - This is not necessarily true. While it's possible for one of the other angles to be a right angle (which would make the other angle 90°), it is not a requirement.

  2. The sum of the measures of the other two angles is 135°. - This statement is true, as we calculated.

  3. The other two angles must be acute angles. - This is not necessarily true. The other two angles could be acute angles, but they also could be one acute angle and one obtuse angle (e.g., 45° and 90°).

  4. One of the other angles must have a measure greater than 90°. - This is not necessarily true, since both angles could also be less than 90° and still sum up to 135° (e.g., 67.5° and 67.5°).

From this analysis, the only conclusion that can be drawn with certainty is:

The sum of the measures of the other two angles is 135°.