Solve Trig Equation A9Be5E
1. **State the problem:** Solve the trigonometric equation $$6 \tan x \sin x = 5 \sin x - \cos x$$ for $$0^\circ \leq x \leq 360^\circ$$.
2. **Rewrite the equation:** Recall that $$\tan x = \frac{\sin x}{\cos x}$$, so substitute:
$$6 \cdot \frac{\sin x}{\cos x} \cdot \sin x = 5 \sin x - \cos x$$
3. **Simplify the left side:**
$$6 \frac{\sin^2 x}{\cos x} = 5 \sin x - \cos x$$
4. **Multiply both sides by $$\cos x$$ to clear the denominator:**
$$6 \sin^2 x = 5 \sin x \cos x - \cos^2 x$$
5. **Bring all terms to one side:**
$$6 \sin^2 x - 5 \sin x \cos x + \cos^2 x = 0$$
6. **Use the Pythagorean identity $$\sin^2 x + \cos^2 x = 1$$ to express $$\sin^2 x$$:**
$$6 (1 - \cos^2 x) - 5 \sin x \cos x + \cos^2 x = 0$$
7. **Expand and simplify:**
$$6 - 6 \cos^2 x - 5 \sin x \cos x + \cos^2 x = 0$$
$$6 - 5 \cos^2 x - 5 \sin x \cos x = 0$$
8. **Rewrite:**
$$6 = 5 \cos^2 x + 5 \sin x \cos x$$
9. **Divide both sides by 5:**
$$\frac{6}{5} = \cos^2 x + \sin x \cos x$$
10. **Factor the right side:**
$$\cos x (\cos x + \sin x) = \frac{6}{5}$$
11. **Note that $$\cos x$$ and $$\cos x + \sin x$$ are bounded between -1 and 1, so check possible values:**
12. **Try to solve by substitution or numerical methods:**
13. **Alternatively, return to step 4 and consider cases:**
- Case 1: $$\sin x = 0$$
Substitute into original equation:
$$6 \tan x \sin x = 0$$ and $$5 \sin x - \cos x = -\cos x$$
So equation becomes $$0 = -\cos x$$, which implies $$\cos x = 0$$.
But $$\sin x = 0$$ and $$\cos x = 0$$ cannot be true simultaneously.
So no solution here.
- Case 2: $$\sin x \neq 0$$, divide original equation by $$\sin x$$:
$$6 \tan x = 5 - \frac{\cos x}{\sin x} = 5 - \cot x$$
14. **Recall $$\tan x = \frac{\sin x}{\cos x}$$ and $$\cot x = \frac{\cos x}{\sin x}$$, so rewrite:**
$$6 \tan x + \cot x = 5$$
15. **Multiply both sides by $$\sin x \cos x$$ to clear denominators:**
$$6 \sin x \cos x + \cos^2 x = 5 \sin x \cos x$$
16. **Bring all terms to one side:**
$$6 \sin x \cos x + \cos^2 x - 5 \sin x \cos x = 0$$
$$\cos^2 x + (6 - 5) \sin x \cos x = 0$$
$$\cos^2 x + \sin x \cos x = 0$$
17. **Factor $$\cos x$$:**
$$\cos x (\cos x + \sin x) = 0$$
18. **Set each factor to zero:**
- $$\cos x = 0$$
- $$\cos x + \sin x = 0$$
19. **Solve $$\cos x = 0$$ for $$0^\circ \leq x \leq 360^\circ$$:**
$$x = 90^\circ, 270^\circ$$
20. **Solve $$\cos x + \sin x = 0$$:**
$$\sin x = -\cos x$$
Divide both sides by $$\cos x$$ (where $$\cos x \neq 0$$):
$$\tan x = -1$$
21. **Find $$x$$ such that $$\tan x = -1$$ in $$0^\circ \leq x \leq 360^\circ$$:**
$$x = 135^\circ, 315^\circ$$
22. **Check all solutions in original equation:**
- For $$x=90^\circ$$, $$\tan 90^\circ$$ is undefined, discard.
- For $$x=270^\circ$$, $$\tan 270^\circ$$ is undefined, discard.
- For $$x=135^\circ$$ and $$315^\circ$$, $$\tan x$$ is defined.
23. **Verify $$x=135^\circ$$:**
$$6 \tan 135^\circ \sin 135^\circ = 6 (-1)(\frac{\sqrt{2}}{2}) = -3 \sqrt{2}$$
$$5 \sin 135^\circ - \cos 135^\circ = 5 (\frac{\sqrt{2}}{2}) - (-\frac{\sqrt{2}}{2}) = 3 \sqrt{2}$$
Not equal, so discard.
24. **Verify $$x=315^\circ$$:**
$$6 \tan 315^\circ \sin 315^\circ = 6 ( -1)(-\frac{\sqrt{2}}{2}) = 3 \sqrt{2}$$
$$5 \sin 315^\circ - \cos 315^\circ = 5 (-\frac{\sqrt{2}}{2}) - (\frac{\sqrt{2}}{2}) = -3 \sqrt{2}$$
Not equal, discard.
25. **Re-examine step 13 case 1:**
If $$\sin x = 0$$, then original equation becomes:
$$6 \tan x \cdot 0 = 5 \cdot 0 - \cos x$$
$$0 = -\cos x$$
$$\cos x = 0$$
No $$x$$ satisfies both $$\sin x=0$$ and $$\cos x=0$$ simultaneously.
26. **Re-examine step 14:**
Equation $$6 \tan x + \cot x = 5$$ can be rewritten as:
$$6 \frac{\sin x}{\cos x} + \frac{\cos x}{\sin x} = 5$$
Multiply both sides by $$\sin x \cos x$$:
$$6 \sin^2 x + \cos^2 x = 5 \sin x \cos x$$
27. **Use $$\sin^2 x = 1 - \cos^2 x$$:**
$$6 (1 - \cos^2 x) + \cos^2 x = 5 \sin x \cos x$$
$$6 - 6 \cos^2 x + \cos^2 x = 5 \sin x \cos x$$
$$6 - 5 \cos^2 x = 5 \sin x \cos x$$
28. **Bring all terms to one side:**
$$6 - 5 \cos^2 x - 5 \sin x \cos x = 0$$
29. **Divide by 5:**
$$\frac{6}{5} - \cos^2 x - \sin x \cos x = 0$$
30. **Rewrite:**
$$\cos^2 x + \sin x \cos x = \frac{6}{5}$$
31. **Note that $$\cos^2 x + \sin x \cos x \leq 1 + 1 = 2$$ but $$\frac{6}{5} = 1.2$$, so solutions may exist.
32. **Try substitution $$t = \cos x$$ and $$s = \sin x$$ with $$s^2 + t^2 = 1$$:**
Equation becomes:
$$t^2 + s t = 1.2$$
33. **Express $$s = \pm \sqrt{1 - t^2}$$ and substitute:**
$$t^2 + t (\pm \sqrt{1 - t^2}) = 1.2$$
34. **Solve for $$t$$ numerically or graphically.**
**Final answer:**
The exact solutions are the $$x$$ values satisfying
$$\cos x (\cos x + \sin x) = \frac{6}{5}$$
within $$0^\circ \leq x \leq 360^\circ$$.
Since $$\frac{6}{5} > 1$$, and $$\cos x (\cos x + \sin x) \leq 1$$, no real solutions exist.
**Therefore, the only solutions come from:**
$$\cos x (\cos x + \sin x) = 0$$
which gives $$x = 90^\circ, 270^\circ$$ (discarded due to undefined $$\tan x$$) and $$x = 135^\circ, 315^\circ$$ (which do not satisfy original equation).
Hence, **no solutions** in $$0^\circ \leq x \leq 360^\circ$$.
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**Summary:**
- No valid $$x$$ satisfies the equation in the given interval.