To determine an unknown angle in a triangle, it is essential to remember that the sum of all interior angles in a triangle is always $180$ degrees.

This property is fundamental to the study of triangles and plays a crucial role in solving problems that involve unknown angles. If you know the measures of two angles in a triangle, you can easily find the third angle by subtracting the sum of the known angles from $180$ degrees. For instance, consider a triangle with angles measuring $50$ degrees and $60$ degrees. The measure of the third angle can be calculated as follows:

Another approach involves utilizing the characteristics of specific types of triangles. For example, in an equilateral triangle, all three angles are congruent, each measuring $60$ degrees. In contrast, in an isosceles triangle, where two angles are equal, you can determine the third angle if you know one of the equal angles. For example, if an isosceles triangle has two angles of $45$ degrees, the measure of the third angle can be found as follows:

In the case of right-angled triangles, one of the angles is always $90$ degrees. If you know one of the other angles, you can find the remaining angle by subtracting the known angle from $90$ degrees. For instance, if one angle in a right-angled triangle measures $30$ degrees, the other angle can be determined as follows:

By employing these methods, you can confidently ascertain the measure of an unknown angle in any triangle.