<P> The length of a degree of longitude (east - west distance) depends only on the radius of a circle of latitude . For a sphere of radius a that radius at latitude φ is a cos φ, and the length of a one - degree (or π / 180 radian) arc along a circle of latitude is </P> <Dl> <Dd> Δ l o n g 1 = π 180 ∘ a cos ⁡ φ (\ displaystyle \ Delta _ (\ rm (long)) ^ (1) = (\ frac (\ pi) (180 ^ (\ circ))) a \ cos \ phi) </Dd> </Dl> <Dd> Δ l o n g 1 = π 180 ∘ a cos ⁡ φ (\ displaystyle \ Delta _ (\ rm (long)) ^ (1) = (\ frac (\ pi) (180 ^ (\ circ))) a \ cos \ phi) </Dd> <Table> <Tr> <Th> φ </Th> <Th> Δ1 lat </Th> <Th> Δ1 long </Th> </Tr> <Tr> <Td> 0 ° </Td> <Td> 110.574 km </Td> <Td> 111.320 km </Td> </Tr> <Tr> <Td> 15 ° </Td> <Td> 110.649 km </Td> <Td> 107.551 km </Td> </Tr> <Tr> <Td> 30 ° </Td> <Td> 110.852 km </Td> <Td> 96.486 km </Td> </Tr> <Tr> <Td> 45 ° </Td> <Td> 111.132 km </Td> <Td> 78.847 km </Td> </Tr> <Tr> <Td> 60 ° </Td> <Td> 111.412 km </Td> <Td> 55.800 km </Td> </Tr> <Tr> <Td> 75 ° </Td> <Td> 111.618 km </Td> <Td> 28.902 km </Td> </Tr> <Tr> <Td> 90 ° </Td> <Td> 111.694 km </Td> <Td> 0.000 km </Td> </Tr> </Table>

Which of the following lines of longitude is also an entire great circle