Question

If a planet subtends an angle α at distance D, what formula is used to find the planet's diameter?

Options

• Diameter = D/2

• Diameter = α × D

• Diameter = α + D

• Diameter = D²/α

Answer 1

Diameter = α × D

Explanation:

Derived from the small-angle approximation, where diameter is analogous to the arc length (arc length = angle × radius).