Trig Quadrant Values
1. **State the problem:** Given $\cos \theta = -\frac{2}{5}$ and $\sin \theta > 0$, find the quadrant of $\theta$ and the values of $\sin \theta$, $\tan \theta$, $\sec \theta$, $\csc \theta$, and $\cot \theta$.
2. **Determine the quadrant:** Since $\cos \theta$ is negative and $\sin \theta$ is positive, $\theta$ lies in Quadrant II where cosine is negative and sine is positive.
3. **Find $\sin \theta$:** Use the Pythagorean identity:
$$\sin^2 \theta + \cos^2 \theta = 1$$
Substitute $\cos \theta = -\frac{2}{5}$:
$$\sin^2 \theta + \left(-\frac{2}{5}\right)^2 = 1$$
$$\sin^2 \theta + \frac{4}{25} = 1$$
$$\sin^2 \theta = 1 - \frac{4}{25} = \frac{25}{25} - \frac{4}{25} = \frac{21}{25}$$
Since $\sin \theta > 0$,
$$\sin \theta = \sqrt{\frac{21}{25}} = \frac{\sqrt{21}}{5}$$
4. **Find $\tan \theta$:**
$$\tan \theta = \frac{\sin \theta}{\cos \theta} = \frac{\frac{\sqrt{21}}{5}}{-\frac{2}{5}} = -\frac{\sqrt{21}}{2}$$
5. **Find $\sec \theta$:**
$$\sec \theta = \frac{1}{\cos \theta} = \frac{1}{-\frac{2}{5}} = -\frac{5}{2}$$
6. **Find $\csc \theta$:**
$$\csc \theta = \frac{1}{\sin \theta} = \frac{1}{\frac{\sqrt{21}}{5}} = \frac{5}{\sqrt{21}} = \frac{5\sqrt{21}}{21}$$
7. **Find $\cot \theta$:**
$$\cot \theta = \frac{1}{\tan \theta} = \frac{1}{-\frac{\sqrt{21}}{2}} = -\frac{2}{\sqrt{21}} = -\frac{2\sqrt{21}}{21}$$
**Final answers:**
- Quadrant: II
- $\sin \theta = \frac{\sqrt{21}}{5}$
- $\tan \theta = -\frac{\sqrt{21}}{2}$
- $\sec \theta = -\frac{5}{2}$
- $\csc \theta = \frac{5\sqrt{21}}{21}$
- $\cot \theta = -\frac{2\sqrt{21}}{21}$