A northeast bearing comes off of the intersection between the y-axis and the x-axis. This intersection is perpendicular; therefore, the angle formed is 90 degrees. Subtract the given angles of 45 and 17 and you are left with 28 degrees. So, plug into the equation:
a² = 1.5² + 3² - 2(1.5)(3)·cos(28)
a² = 2.25 + 9 - 9·cos(28)
a² = 11.25 - 9·cos(28)
a² = 11.25 -7.946...
a² = 3.3...
a = 1.8. Pick option 2.