[math]\LARGE \begin{eqnarray}[br]\sin(\alpha)=\frac a c & \left (= \frac{\text{opposite}}{\text{hypotenuse}}\right )\\[br]\cos(\alpha)=\frac b c & \left (= \frac{\text{adjacent}}{\text{hypotenuse}}\right )\\[br]\tan(\alpha)=\frac a b & \left (= \frac{\text{opposite}}{\text{adjacent}}\right )\\[br]\end{eqnarray}[br][/math][br]

Trigonometric basic formulas help in solving the angle of an right-angled triangle. These basic formulas given you above.   [br][br][br][br][br][color=#3366ff][b]Example 2[/b][/color]. [i]The hypotenuse of a right-angled triangle is 398 and one of the acute angles is  76.4°. Define the legs.[/i][br][br]

The opposite leg can be solved with sine as [br][br]    [math] \sin(76.4\degree)=\frac{y}{398} \;\;\Leftrightarrow\;\; y=398\cdot \sin(76.4\degree)\approx387[/math][br][br]The adjacent leg can be solved with cosine: [br][br]  [math] \cos(76.4\degree)=\frac{x}{398} \;\;\Leftrightarrow\;\; x=398\cdot \cos(76.4\degree)\approx 94[/math][br]     [br]