HINT:#
The question is asking for the distance traveled by a knot moving at constant velocity.
HINT:#
The problem tells us what the rate of travel is per unit time (velocity) and the length of time over which we want to calculate the distance traveled by the knot.
HINT:#
The distance to the knot is equal to
d = L / theta Picture Hint
Where L is the distance that the object moved in 10 years, and theta is the number of degrees the object was observed to move across the sky during those years.

NOTE: This formula uses the approximation that when angle θ is small, sin(θ) ≈ θ.
HINT:#
L = 1.58 x 1012 km
theta = 3 arc seconds
HINT:#
Let's use unit analysis:
d(km) = L(km)/sin(theta) ~ L(km)/theta(radians)
Since we want our answer in kilometers, we will have to convert arcseconds to radians.

3 arc-seconds * 1 radian/206,265 arcseconts = 1.45 x 10-5 radians
HINT:#
d = 1.58 x 1012 km / 1.45 x 10-5 = 1.1 x 1017 km

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