0\\sin\alpha=\sqrt{1-cos^2\alpha}\\sin\alpha=\sqrt{1-(-\frac{\sqrt{15}}{4})^2}\\sin\alpha=\sqrt{1-\frac{15}{16}}\\sin\alpha=\sqrt{\frac{1}{16}}\\sin\alpha=\frac{1}{4}" alt="cos\alpha=-\frac{\sqrt{15}}{4}\\sin\alpha>0\\sin\alpha=\sqrt{1-cos^2\alpha}\\sin\alpha=\sqrt{1-(-\frac{\sqrt{15}}{4})^2}\\sin\alpha=\sqrt{1-\frac{15}{16}}\\sin\alpha=\sqrt{\frac{1}{16}}\\sin\alpha=\frac{1}{4}" align="absmiddle" class="latex-formula">