回復 1# thepiano 的帖子
不知道這樣算有沒有比較快ㄧ些？
\(\displaystyle \frac{1}{2}sinx \cdot (3-4sin^2 16^{\circ})=sin44^{\circ}\cdot sin(106^{\circ}-x)\)
\(\displaystyle \frac{sinx}{sin(106^{\circ}-x)}=\frac{2 \times sin44^{\circ}}{3-4\times (\frac{1-cos32^{\circ}}{2})}\)
\(\displaystyle \frac{sinx}{sin(106^{\circ}-x)}=\frac{2sin44^{\circ}}{1+2cos32^{\circ}}\)
\(\displaystyle \frac{sinx}{sin(106^{\circ}-x)}=\frac{sin44^{\circ}}{cos60^{\circ}+cos32^{\circ}}\)
\(\displaystyle \frac{sinx}{sin(106^{\circ}-x)}=\frac{sin44^{\circ}}{2cos46^{\circ}cos14^{\circ}}\)
\(\displaystyle \frac{sinx}{sin(106^{\circ}-x)}=\frac{sin30^{\circ}}{sin76^{\circ}}\)
\(x=30^{\circ}\)
