Final answer:
In a 10 degree caudal projection of the coccyx, the coccyx appears below the symphysis pubis due to the downward caudal tilt of the X-ray beam in relation to the orientation of the pelvis.
Step-by-step explanation:
On a 10 degree caudal projection of the coccyx, the coccyx is demonstrated below the symphysis pubis. The caudal projection tilts the X-ray beam at a downward angle, targeting the area beneath the pelvis. As the coccyx is located at the posterior end of the pelvis, articulating with the inferior tip of the sacrum, and since the beam is angled caudally, the coccyx will appear below the pubic symphysis on the image. The symphysis pubis joins the two pubic bodies and is positioned more anteriorly compared to the coccyx. The relative positions of the coccyx and symphysis pubis are such that in the caudal tilt, the symphysis is projected superiorly and the coccyx inferiorly in the X-ray image.