1. **State the problem:** Given that $\sin A = \frac{5}{3}$ and $A$ is in the second quadrant, find $\cos 2A$ and $\sin 2A$.
2. **Note:** The value $\sin A = \frac{5}{3}$ is not possible since sine values must be between -1 and 1. Assuming a typo and the correct value is $\sin A = \frac{3}{5}$.
3. **Recall quadrant rules:** In the second quadrant, sine is positive and cosine is negative.
4. **Find $\cos A$ using Pythagorean identity:**
$$\sin^2 A + \cos^2 A = 1$$
$$\left(\frac{3}{5}\right)^2 + \cos^2 A = 1$$
$$\frac{9}{25} + \cos^2 A = 1$$
$$\cos^2 A = 1 - \frac{9}{25} = \frac{16}{25}$$
Since $A$ is in the second quadrant, $\cos A = -\frac{4}{5}$.
5. **Use double angle formulas:**
$$\cos 2A = \cos^2 A - \sin^2 A$$
$$\sin 2A = 2 \sin A \cos A$$
6. **Calculate $\cos 2A$:**
$$\cos 2A = \left(-\frac{4}{5}\right)^2 - \left(\frac{3}{5}\right)^2 = \frac{16}{25} - \frac{9}{25} = \frac{7}{25}$$
7. **Calculate $\sin 2A$:**
$$\sin 2A = 2 \times \frac{3}{5} \times \left(-\frac{4}{5}\right) = -\frac{24}{25}$$
**Final answers:**
$$\cos 2A = \frac{7}{25}$$
$$\sin 2A = -\frac{24}{25}$$
Double Angle Values E1Dbee
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