To determine the measure of the third angle in a triangle when the measures of the other two angles are given, follow these steps:
1. Recall that the sum of the angles in any triangle is always 180°.
2. You are given the measures of two angles:
- The first angle is 25°
- The second angle is 55°
3. To find the measure of the third angle, subtract the sum of the two known angles from 180°, as follows:
[tex]\[
\text{Measure of the third angle} = 180° - (\text{First angle} + \text{Second angle})
\][/tex]
4. Substitute the given angles into the equation:
[tex]\[
\text{Measure of the third angle} = 180° - (25° + 55°)
\][/tex]
5. Calculate the sum of the first two angles:
[tex]\[
25° + 55° = 80°
\][/tex]
6. Subtract this sum from 180°:
[tex]\[
180° - 80° = 100°
\][/tex]
Thus, the measure of the third angle is 100°.
Now, let's match our calculated measure with the given choices:
- OA. 80°
- OB. 30°
- OC. 100°
- OD. 135°
The correct answer is:
OC. 100°
Therefore, the measure of the third angle is 100°.
