## University Calculus: Early Transcendentals (3rd Edition)

$59.5^{ \circ}$
The formula to calculate the angle between the vector v and the x-axis is: $\theta = \cos ^{-1} (\dfrac{v_x}{|v|})$ Here, $v=\lt 3,-5,1 \gt$ $|v|=\sqrt{3^2+(-5)^2+(1)^2}= \sqrt {35}$ Thus, $\theta = \cos ^{-1} (\dfrac{v_x}{|v|})=\cos ^{-1} (\dfrac{3}{ \sqrt {35}})$ or, $\theta =59.5^{ \circ}$