Find the coordinates of the point on the unit circle corresponding to the angle whose cosine is $-frac{2}{3}$.
Answer 1
Given the cosine of the angle is $-\frac{2}{3}$,
First, find the sine of the angle using the Pythagorean identity:
$\cos^2\theta + \sin^2\theta = 1$
Substitute $\cos\theta = -\frac{2}{3}$:
$\left(-\frac{2}{3}\right)^2 + \sin^2\theta = 1$
$\frac{4}{9} + \sin^2\theta = 1$
$\sin^2\theta = 1 – \frac{4}{9}$
$\sin^2\theta = \frac{9}{9} – \frac{4}{9}$
$\sin^2\theta = \frac{5}{9}$
Taking the square root,
$\sin\theta = \pm\sqrt{\frac{5}{9}}$
$\sin\theta = \pm\frac{\sqrt{5}}{3}$
Thus, the coordinates are:
$(-\frac{2}{3}, \frac{\sqrt{5}}{3})$ or $(-\frac{2}{3}, -\frac{\sqrt{5}}{3})$
Answer 2
To find the coordinates of the point on the unit circle where the cosine is $-frac{2}{3}$, we use the Pythagorean identity:
$cos^2 heta + sin^2 heta = 1$
Substituting $cos heta = -frac{2}{3}$:
$left(-frac{2}{3}
ight)^2 + sin^2 heta = 1$
$frac{4}{9} + sin^2 heta = 1$
$sin^2 heta = 1 – frac{4}{9}$
$sin^2 heta = frac{5}{9}$
Taking the square root:
$sin heta = pmfrac{sqrt{5}}{3}$
Therefore, the coordinates are:
$(-frac{2}{3}, frac{sqrt{5}}{3})$ or $(-frac{2}{3}, -frac{sqrt{5}}{3})$
Answer 3
Given $cos heta = -frac{2}{3}$, use the identity:
$cos^2 heta + sin^2 heta = 1$
Substitute $cos heta = -frac{2}{3}$:
$left(-frac{2}{3}
ight)^2 + sin^2 heta = 1$
$frac{4}{9} + sin^2 heta = 1$
$sin^2 heta = frac{5}{9}$
$sin heta = pmfrac{sqrt{5}}{3}$
Coordinates:
$(-frac{2}{3}, frac{sqrt{5}}{3})$ or $(-frac{2}{3}, -frac{sqrt{5}}{3})$
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