4-What determines the length of a planet's day? *

A. tilt
B. orbit
C. moons
D. rotation

Axis rotation to determine the length of a day

Explanation:

The length of time it takes a planet to complete one full rotation on it's axis is what we would measure as being one day. On Earth, it takes slightly less than 24 hours to rotate on its axis and this is one day.

see the picture for the vector

the magnitude of the vector by pythagorean theorem

r = √( (-10)^2 + (3)^2 ) = √109

magnitude = √109 units

the direction angle between vector and x-axis is

tan^(-1)(3/10) = 16.699

so the direction is approximately 16.7 degrees north of west