The Martian moon Phobos orbits near the equatorial plane of Mars in just over 7.5 hours in the same direction as the planet rotation. How then would you see Phobos move across the Martian sky from the surface of the planet

Explanation:

Phobos and Deimos are two moons of the Martian planet. Since both Phobos and Deimos move make their locus along the Martian equator, they can be better seen at planet's equatorial region. If we look Phobos from the planet earth, it would appear bigger than Deimos because of its relative larger size, if might also look almost 1/3rd size of moon of earth. And when seen from Martian equator, Phobos would be seen more as it is faster than Deimos

Phobos will be seen moving across the Martian sky from the surface of the planet that seems thit rises in the west, move across the sky in 4 hours and 15 minutes or less, and set in the east, twice each Martian day.

Explanation:

Phobos is one of the two Martian moon. The second and outer moon of mars is known as Deimos. It is irregular in shape and comparably small in size. It is so close that it orbits Mars much faster than Mars rotates, and completes an orbit in about 7 hours and 30 minutes. Because of the speed of phobos's orbits around the planet equatorial plan, If appears to rise in the west, move across the sky in 4 hours and 15 minutes or less, and set in the east, twice each Martian day, from the surface of Mars.

the answer would be the third option, "no, ariel should have added 9^2 and 12^2 and compared that to 15^2."

this is found through the pythagorean theorem, which is a^2 + b^2 = c^2.

this is the correct way of solving the problem:

9^2 + 12^2 = 15^2

81 + 144 = 225

225 = 225