三角比（直角三角形）

解答 · SOLUTION

1. 1.
   $30^{\circ }$ の正弦は決まった値で $\frac{1}{2}$ です。The sine of $30^{\circ }$ is the standard value $\frac{1}{2}$.

解答 · SOLUTION

1. 1.
   $\sin \theta =\frac{\text{opp}}{\text{hyp}}$ より、$\text{opp}=10\sin 30^{\circ }$。From $\sin \theta =\frac{\text{opp}}{\text{hyp}}$, $\text{opp}=10\sin 30^{\circ }$.
2. 2.
   $=10\times \frac{1}{2}=5$。$=10\times \frac{1}{2}=5$.

解答 · SOLUTION

1. 1.
   $\sin \theta =\frac{\text{opp}}{\text{hyp}}=\frac{5}{10}=\frac{1}{2}$。$\sin \theta =\frac{\text{opp}}{\text{hyp}}=\frac{5}{10}=\frac{1}{2}$.
2. 2.
   $\theta ={\sin }^{-1}\frac{1}{2}=30^{\circ }$。$\theta ={\sin }^{-1}\frac{1}{2}=30^{\circ }$.