Chapter 8 - Complex Numbers, Polar Equations, and Parametric Equations - Section 8.6 Parametric Equations, Graphs, and Applications - 8.6 Exercises - Page 403: 6

$(x,y) = (\frac{\sqrt{2}}{2}, \frac{\sqrt{2}}{2})$, which matches up with option (D)

$x = cos~t$ $y = sin~t$ When $t = \frac{\pi}{4}$: $x = cos~(\frac{\pi}{4}) = \frac{\sqrt{2}}{2}$ $y = sin~(\frac{\pi}{4}) = \frac{\sqrt{2}}{2}$ Then $(x,y) = (\frac{\sqrt{2}}{2}, \frac{\sqrt{2}}{2})$, which matches up with option (D)