1. **State the problem:** Solve the trigonometric equation $3 \sin \theta - 4 \cos \theta = 2$ for $\theta$.
2. **Formula and approach:** We use the identity that any expression of the form $a \sin \theta + b \cos \theta$ can be rewritten as $R \sin(\theta + \alpha)$ where $R = \sqrt{a^2 + b^2}$ and $\alpha$ satisfies $\cos \alpha = \frac{a}{R}$, $\sin \alpha = \frac{b}{R}$.
3. **Calculate $R$:**
$$
R = \sqrt{3^2 + (-4)^2} = \sqrt{9 + 16} = \sqrt{25} = 5
$$
4. **Find $\alpha$:**
$$
\cos \alpha = \frac{3}{5}, \quad \sin \alpha = \frac{-4}{5}
$$
Since $\sin \alpha$ is negative and $\cos \alpha$ positive, $\alpha$ is in the fourth quadrant.
5. **Rewrite the equation:**
$$
3 \sin \theta - 4 \cos \theta = 5 \sin(\theta - \alpha) = 2
$$
6. **Solve for $\sin(\theta - \alpha)$:**
$$
\sin(\theta - \alpha) = \frac{2}{5}
$$
7. **Find general solutions:**
$$
\theta - \alpha = \sin^{-1}\left(\frac{2}{5}\right) \quad \text{or} \quad \theta - \alpha = \pi - \sin^{-1}\left(\frac{2}{5}\right)
$$
8. **Calculate $\sin^{-1}(2/5)$ approximately:**
$$
\sin^{-1}\left(\frac{2}{5}\right) \approx 0.4115
$$
9. **Recall $\alpha$:**
$$
\alpha = \arctan\left(\frac{-4}{3}\right) \approx -0.9273
$$
10. **Find $\theta$ values:**
$$
\theta = 0.4115 - (-0.9273) = 1.3388
$$
$$
\theta = \pi - 0.4115 - (-0.9273) = 3.6574
$$
11. **Final answer:**
$$
\theta \approx 1.34 \text{ radians or } 3.66 \text{ radians (plus } 2k\pi \text{ for any integer } k)
$$
Solve Trig Equation C50951
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