Final answer:
To confirm that a transformation is not a rigid motion, use a protractor to check for any changes in angles within a shape post-transformation. If the angles have changed, the transformation is not rigid. Corresponding side length changes further confirm this.
Step-by-step explanation:
To confirm that a transformation is not a rigid motion using a protractor, you must look for changes in the shape's size or the angles between any two adjacent sides. A rigid motion, also known as an isometry, will preserve distances and angles between all points on a shape. Therefore, if after a transformation, using a protractor shows that the angles within the shape have changed, or that the corresponding sides are not congruent, then the transformation is not a rigid motion.
For example, if you have a triangle and apply a transformation, such as dilation or shearing, the new angles can be measured with a protractor. If they are different from the original triangle's angles, this confirms the transformation was not a rigid motion. Additionally, if the distances between corresponding points on the figure have changed, which you can measure with a ruler, this also confirms that the transformation is not rigid.