Plane angle and solid angle have:

• A: units but no dimensions
• B: dimensions but no units
• C: no units and no dimensions
• D: both units and dimensions

Plane angles and solid angles are both types of angles used in geometry, but they differ in their characteristics.

Understanding Plane Angles

A plane angle is formed by two rays that share a common endpoint. The unit of measurement for plane angles is typically degrees (°) or radians (rad). However, plane angles do not have dimensions in the sense of physical quantities like length or mass.

Characteristics of Plane Angles

• Units: Degrees or radians
• Dimensions: None

Exploring Solid Angles

A solid angle, on the other hand, is the three-dimensional counterpart of a plane angle. It is measured in steradians (sr). Similar to plane angles, solid angles do not possess dimensions.

Key Features of Solid Angles

• Units: Steradians
• Dimensions: None

Final Thoughts

Both plane angles and solid angles have units of measurement but lack dimensions. Therefore, the correct answer is:

A: units but no dimensions