Suppose that point $P \left( \frac { \sqrt { 5 } } { 5 } , - \frac { 2 \sqrt { 5 } } { 5 } \right)$ is on the unit circle. Find $\sin t$ and $\cos t$
A) $\sin t = - \frac { 2 \sqrt { 5 } } { 5 } , \quad \cos t = \frac { \sqrt { 5 } } { 5 }$
B) $\sin t = - \frac { \sqrt { 5 } } { 5 } , \quad \cos t = \frac { \sqrt { 5 } } { 5 }$
C) $\sin t = \frac { \sqrt { 5 } } { 5 } , \quad \cos t = - \frac { 2 \sqrt { 5 } } { 5 }$
D) $\sin t = 2 \sqrt { 5 } , \cos t = \frac { \sqrt { 5 } } { 5 }$
E) none of these

Question

Quizplus · Accepted Answer

For a point $(x, y)$ on the unit circle, $x = \cos t$ and $y = \sin t$. Therefore, $\cos t = \frac{\sqrt{5}}{5}$ and $\sin t = -\frac{2\sqrt{5}}{5}$.

Suppose That Point P(55,−255)P \left( \frac { \sqrt { 5 } } { 5 } , - \frac { 2 \sqrt { 5 } } { 5 } \right)P(55​​,−525​​)

Suppose That Point $P \left( \frac { \sqrt { 5 } } { 5 } , - \frac { 2 \sqrt { 5 } } { 5 } \right)$