第13章 13.24

cos⁡(x+23π)+sin⁡(x+π4)=(cos⁡x⋅cos⁡23π−sin⁡x⋅sin⁡23π)+(sin⁡x⋅cos⁡π4+cos⁡x⋅sin⁡π4)\cos\left(x+\frac{2}{3}\pi\right)+\sin\left(x+\frac{\pi}{4}\right)=\left(\cos x\cdot\cos\frac{2}{3}\pi-\sin x\cdot\sin\frac{2}{3}\pi\right)+\left(\sin x\cdot\cos\frac{\pi}{4}+\cos x\cdot\sin\frac{\pi}{4}\right)

=−12cos⁡x−32sin⁡x+12sin⁡x+12cos⁡x=-\frac{1}{2}\cos x-\frac{\sqrt{3}}{2}\sin x+\frac{1}{\sqrt{2}}\sin x+\frac{1}{\sqrt{2}}\cos x

=2−12cos⁡x+2−32sin⁡x=\frac{\sqrt{2}-1}{2}\cos x+\frac{\sqrt{2}-\sqrt{3}}{2}\sin x

解説: r31bn1z