This question tests understanding that reflections preserve individual angle measures, keeping relationships like supplementary. Angles 110° and 70° are reflected to 110° and 70°, still supplementary as measures are unchanged. Example: 90° and 90° reflected remain 90° each. Specifically, after x-axis reflection, ∠1'=110° and ∠2'=70°, summing to 180°. True statement: they are 110° and 70°, still supplementary. Errors: thinking reflection swaps or changes to non-supplementary. Verification: originals 110°,70°, apply reflection, images same measures, preserved; relationships hold due to isometry.

This question tests understanding that reflections, a rigid transformation, preserve angle measures by flipping the figure but not changing angle sizes. Angle DEF with measure 120° is reflected across the y-axis to form angle D'E'F' with measure 120° unchanged, whether flipped or not, as the spread between rays remains the same. For instance, a right angle of 90° reflected over an axis is still 90°, oriented differently but with the same measure. Specifically, reflecting angle DEF=120° over the y-axis changes coordinates (e.g., points mirror), but measuring the angle at the new vertex gives 120°. The correct preservation is that the image angle equals the original, as reflections are isometries. Errors include claiming reflection inverts the measure (e.g., 120° becomes -120° or 60°), confusing sign with size. Verification: original 120°, apply reflection, image measures 120°, preserved; all rigid transformations maintain angles via distance preservation.

This question tests understanding that rotations, rigid transformations, preserve angle measures by turning the figure but not altering angle sizes. Angle JKL with measure 90° is rotated 45° counterclockwise about K to form angle J'K'L' with measure 90° unchanged, as rotation affects orientation but not the ray spread. Example: a 90° angle rotated 45° remains 90°, just pointing differently. Here, rotating the right angle 45° CCW about the vertex keeps the measure at 90° in the image. Correctly, the image angle equals the original due to rotation's isometry property. Common mistakes: adding rotation amount to the measure (90° +45°=135°), thinking it changes size. Verification: original 90°, apply 45° rotation, image measures 90°, preserved; angles depend on preserved distances.

This question tests understanding that reflections preserve angle measures, not flipping to supplements. Angle GHI=60° reflected forms G'H'I'=60°, unchanged despite flip. Example: 90° reflected stays 90°. Specifically, the image angle is 60°. Incorrect; still 60° because reflection preserves measure. Errors: claiming it becomes supplement (120°) or 0°. Verification: original 60°, apply reflection, image 60°, preserved; mistakes like confusing flip with size inversion.

This question tests understanding that rotations, reflections, and translations preserve angle measures—rigid transformations change position or orientation but not angle size. Angle measure is preserved under rigid transformations: angle GHI with measure 30° transforms to G'H'I' with 30° (unchanged) whether rotated (turned), reflected (flipped), or translated (shifted). The measure depends on the spread between rays forming the angle, not position or orientation—moving or rotating the angle doesn't change the 'openness' or degree measure. Specific to reflection: 30° acute angle reflected remains 30° acute, not becoming obtuse. The correct comparison is that it measures 30° because reflections preserve angle measure. A common error is claiming reflection inverts to 150° or -30°, or depends on the line (but preservation is general). Verification: original 30°, apply reflection, image 30°, all rigid transformations preserve as they are isometries.

This question tests understanding that rotations, reflections, and translations preserve angle measures—rigid transformations change position or orientation but not angle size. Angle measure is preserved under rigid transformations: angles in triangle PQR (40°, 60°, 80°) transform to P'Q'R' with the same measures (unchanged) whether rotated (turned), reflected (flipped), or translated (shifted). The measure depends on the spread between rays forming the angle, not position or orientation—moving or rotating the angle doesn't change the 'openness' or degree measure. Multiple angles: triangle with 40°, 60°, 80° reflected maintains all three measures, summing to 180° before and after. The correct preservation is that P'Q'R' has angles 40°, 60°, 80°, as rigid transformations keep individual angles identical. Errors include altering measures, like to 50°, 60°, 70°, perhaps confusing with non-rigid changes. Verification: original angles 40°, 60°, 80°, apply reflection, image same, preserved because isometries maintain distances and angles.

This question tests understanding that translations, a type of rigid transformation, preserve angle measures by changing position but not the size or shape of the angle. Angle ABC with measure 50° is translated to form angle A'B'C' with measure 50° unchanged, as translation simply shifts the angle without altering the spread between its rays. For example, a right angle of 90° translated horizontally remains 90°, just in a new location but with identical measure. In this specific case, translating angle ABC=50° by 6 units right and 2 units up results in angle A'B'C'=50°, as the coordinates change but the angle at the vertex stays the same. The correct answer is that the measure is preserved at 50°, a property of rigid transformations. A common error is thinking translation affects angles, like adding the shift amounts to the measure (e.g., 50° + 6° + 2° =58°), but it doesn't change the 'openness'. To verify, measure original angle ABC=50°, apply translation to points, measure image angle A'B'C'=50°, confirming preservation since distances are maintained.

This question tests understanding that rotations, reflections, and translations preserve angle measures—rigid transformations change position or orientation but not angle size. Angle measure is preserved under rigid transformations: angle DEF with measure 120° transforms to D'E'F' with measure 120° (unchanged) whether rotated (turned), reflected (flipped), or translated (shifted). The measure depends on the spread between rays forming the angle, not position or orientation—moving or rotating the angle doesn't change the 'openness' or degree measure. Specific to reflection: angle DEF = 120° reflected over the y-axis to D'E'F', coordinates change but the angle at the vertex still measures 120°. The correct preservation is that the image angle equals the original, as rigid transformations maintain angle measures. A common error is claiming reflection inverts the size, like choosing 60° (supplementary) or -120° (confusing direction), but the measure stays positive and unchanged. To verify: measure original (120°), apply reflection (flips but preserves spread), measure image (120°), all rigid transformations preserve because they are isometries.

This question tests understanding that translations preserve angle measures by shifting without changing size. Angle STU=45° is translated 10 units left to form S'T'U' with the same 45° measure, as position change doesn't affect ray spread. Example: 90° translated left remains 90°. Specifically, after left shift, the image angle measures 45°. It is the same because translation preserves angle measure. Errors: thinking movement left increases/decreases measure or makes rays separate to 0°. Verification: original 45°, apply translation, image 45°, preserved; rigid transformations maintain angles via isometry.

This question tests understanding that reflections preserve angle measures in triangles, as rigid transformations maintain all angles. Triangle PQR with angles 40°, 60°, 80° is reflected to form P'Q'R' with the same 40°, 60°, 80° measures, unchanged despite flipping. For example, a triangle with 90°, 45°, 45° reflected keeps those exact angles. Specifically, after reflection, P'Q'R' has angles 40°, 60°, 80°, as individual measures are preserved. Correctly, the set of angles remains identical, summing to 180° before and after. Errors: thinking reflection alters angles to new sets like 40°, 60°, 90°. Verification: original angles 40°,60°,80°, apply reflection, image angles same, preserved; multiple angles stay exact under isometries.