Question

= exterior angle- (图)

Explanation:

Step1: Recall Exterior Angle Theorem

The exterior angle theorem states that an exterior angle of a triangle is equal to the sum of the two non - adjacent interior angles. In the given diagram, \(\angle ACD\) (or \(\angle BCD\) depending on the labeling, but in general, the exterior angle at \(C\)) is equal to \(\angle A+\angle B\).

Step2: Identify the Angles

In triangle \(ABC\), when we extend side \(AC\) to \(D\), \(\angle BCD\) (the exterior angle) is formed. The two non - adjacent interior angles to \(\angle BCD\) are \(\angle A\) and \(\angle B\). So, by the exterior angle theorem, \(\angle BCD=\angle A + \angle B\).

Answer:

The measure of the exterior angle (e.g., \(\angle BCD\)) is equal to the sum of the measures of the two non - adjacent interior angles (i.e., \(\angle A+\angle B\))