Maritza draw a rectangle on the coordinate plane and labels the verticals A, B, C, and D. She’s then reflects to figure across the X axis to get rectangle A’ B’ C’ D’. What is the measure of angle D’ in the reflected rectangle? Angle D’ measures how many degrees?
When a figure is reflected across the X-axis, the y-coordinates of each point are changed to their negatives. Since a rectangle has opposite angles that are congruent, the measure of angle D' in the reflected rectangle is the same as the measure of angle D in the original rectangle. Thus, the measure of angle D' is equal to the measure of angle D, which is equal to 90 degrees (since a rectangle has four right angles). Therefore, angle D' measures 90 degrees.
