Dy Dx Stationary
1. **State the problem:** We have the curve defined by $$y = \frac{e^{\sin x}}{\cos^2 x}$$ for $$0 \leq x \leq 2\pi$$. We need to find $$\frac{dy}{dx}$$ and then find the $$x$$-coordinates of the stationary points where $$\frac{dy}{dx} = 0$$.
2. **Differentiate using the quotient rule:** Let $$u = e^{\sin x}$$ and $$v = \cos^2 x$$.
The quotient rule states:
$$\frac{dy}{dx} = \frac{v \frac{du}{dx} - u \frac{dv}{dx}}{v^2}$$
3. **Find $$\frac{du}{dx}$$:**
$$u = e^{\sin x}$$
Using chain rule:
$$\frac{du}{dx} = e^{\sin x} \cdot \cos x$$
4. **Find $$\frac{dv}{dx}$$:**
$$v = \cos^2 x = (\cos x)^2$$
Using chain rule:
$$\frac{dv}{dx} = 2 \cos x \cdot (-\sin x) = -2 \cos x \sin x$$
5. **Substitute into quotient rule:**
$$\frac{dy}{dx} = \frac{\cos^2 x \cdot e^{\sin x} \cos x - e^{\sin x} \cdot (-2 \cos x \sin x)}{\cos^4 x}$$
Simplify numerator:
$$e^{\sin x} \cos x \left( \cos^2 x + 2 \sin x \right)$$
So:
$$\frac{dy}{dx} = \frac{e^{\sin x} \cos x (\cos^2 x + 2 \sin x)}{\cos^4 x} = e^{\sin x} \frac{\cos^2 x + 2 \sin x}{\cos^3 x}$$
6. **Find stationary points:** Set $$\frac{dy}{dx} = 0$$.
Since $$e^{\sin x} \neq 0$$ and $$\cos^3 x \neq 0$$ except where undefined, the numerator must be zero:
$$\cos^2 x + 2 \sin x = 0$$
Rewrite:
$$\cos^2 x = -2 \sin x$$
Using $$\cos^2 x = 1 - \sin^2 x$$:
$$1 - \sin^2 x = -2 \sin x$$
Rearranged:
$$\sin^2 x - 2 \sin x - 1 = 0$$
7. **Solve quadratic in $$\sin x$$:**
Let $$s = \sin x$$:
$$s^2 - 2s - 1 = 0$$
Use quadratic formula:
$$s = \frac{2 \pm \sqrt{4 + 4}}{2} = 1 \pm \sqrt{2}$$
8. **Check valid solutions:**
$$1 + \sqrt{2} > 1$$ (not possible for sine)
$$1 - \sqrt{2} \approx -0.414$$ (valid)
So:
$$\sin x = 1 - \sqrt{2}$$
9. **Find $$x$$ in $$[0, 2\pi]$$:**
$$x = \arcsin(1 - \sqrt{2})$$ and $$x = \pi - \arcsin(1 - \sqrt{2})$$
**Final answers:**
$$\frac{dy}{dx} = e^{\sin x} \frac{\cos^2 x + 2 \sin x}{\cos^3 x}$$
Stationary points at $$x = \arcsin(1 - \sqrt{2})$$ and $$x = \pi - \arcsin(1 - \sqrt{2})$$ within $$0 \leq x \leq 2\pi$$.