Mathematics

Problem

The position of a particle in space is

\mathbf r(t)=\langle \sin t,\,\cos t,\, t\rangle

for

0\le t\le 2\pi

. For which value(s) of

t

in this interval are the velocity and acceleration vectors orthogonal? a)

t=\dfrac{\pi}{2}

only b)

t=0,\,\pi,\,2\pi

c) Every

t

[0,2\pi]

d) No value of

t

[0,2\pi]