Chapter 13 - Vector Geometry - 13.7 Cylindrical and Spherical Coordinates - Exercises - Page 699: 1

$(4, \pi,4) \Longrightarrow (-4, 0,4) $.

We have $$ r=4, \quad \theta =\pi, \quad z=4.$$ Now, we have $$ x=r\cos \theta=4 \cos \pi =-4,$$ $$ y=r\sin \theta=4 \sin \pi =0,$$ $$ z=z=4.$$ So, $(4, \pi,4) \Longrightarrow (-4, 0,4) $.