г) y = -sin(x+π/4) при x = -15π/4.

Подставим значение $$x = -\frac{15\pi}{4}$$ в функцию $$y = -sin(x+\frac{\pi}{4})$$.

$$y = -sin(-\frac{15\pi}{4} + \frac{\pi}{4}) = -sin(-\frac{14\pi}{4}) = -sin(-\frac{7\pi}{2})$$

$$-\frac{7\pi}{2} = -3\pi - \frac{\pi}{2}$$

$$sin(-\frac{7\pi}{2}) = sin(-3\pi - \frac{\pi}{2}) = -sin(3\pi + \frac{\pi}{2}) = -sin(\pi + \frac{\pi}{2}) = -(-1) = 1$$

$$y = -sin(-\frac{7\pi}{2}) = -1$$

Ответ: y = -1