1. **State the problem:** Solve the trigonometric equation $$7\cos(x) - 5\sin(x) = 5$$ for $x$.
2. **Use the formula:** We can express $a\cos(x) + b\sin(x)$ as $R\cos(x - \alpha)$ where $$R = \sqrt{a^2 + b^2}$$ and $$\tan(\alpha) = \frac{b}{a}$$.
3. **Calculate $R$ and $\alpha$:**
$$R = \sqrt{7^2 + (-5)^2} = \sqrt{49 + 25} = \sqrt{74}$$
$$\tan(\alpha) = \frac{-5}{7}$$
4. **Rewrite the equation:**
$$7\cos(x) - 5\sin(x) = R\cos(x - \alpha) = 5$$
5. **Divide both sides by $R$:**
$$\frac{R\cos(x - \alpha)}{\cancel{R}} = \frac{5}{\cancel{R}} \Rightarrow \cos(x - \alpha) = \frac{5}{\sqrt{74}}$$
6. **Solve for $x - \alpha$:**
$$x - \alpha = \pm \arccos\left(\frac{5}{\sqrt{74}}\right) + 2k\pi, \quad k \in \mathbb{Z}$$
7. **Find $\alpha$:**
$$\alpha = \arctan\left(\frac{-5}{7}\right)$$
8. **Final solution:**
$$x = \alpha \pm \arccos\left(\frac{5}{\sqrt{74}}\right) + 2k\pi, \quad k \in \mathbb{Z}$$
This gives all solutions for $x$ in terms of $k$.
Trig Equation Bd56D7
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