Find the direction of u=-3i+8j (round to the nearest tenth)

keeping in mind that the range of the inverse tangent function is from π/2 to -π/2, that gives us an angle in the IV Quadrant, however, notice "a" and "b", "a" is negative and "b" is positive, that means the II Quadrant.

so we're looking for a reference angle of 69.4° on the II Quadrant, and that'd be 180° - 69.4°, or 110.6°.

Horizontal change or the change of x