Analytische Geometrie-Vektorrechung in der Ebene-Skalarprodukt - Fläche - Winkel
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Beispiel Nr: 03
$\begin{array}{l}
\text{Gegeben:} \\ \text{Vektoren: }
\vec{A} =\left(
\begin{array}{c}
x_a \\
y_a \\
\end{array}
\right) \quad \vec{B} =\left(
\begin{array}{c}
x_b \\
y_b \\
\end{array}
\right) \\
\\ \text{Gesucht:} \\ \text{Länge der Vektoren:} \\ \text{Fläche des Parallelogramms} \\
\text{Skalarprodukt} \\
\\ \\ \textbf{Gegeben:} \\
\text{Vektor: }
\vec{A} =\left(
\begin{array}{c}
\frac{3}{10} \\
1\frac{1}{5} \\
\end{array}
\right) \quad \vec{B} =\left(
\begin{array}{c}
2\frac{2}{5} \\
6 \\
\end{array}
\right) \\
\\ \\ \textbf{Rechnung:} \\
\text{Vektoren: }
\vec{a} =\left(
\begin{array}{c}
\frac{3}{10} \\
1\frac{1}{5} \\
\end{array}
\right) \quad \vec{b} =\left(
\begin{array}{c}
2\frac{2}{5} \\
6 \\
\end{array}
\right) \\
\bullet \text{Steigung} \\
m_s=\dfrac{y_a}{x_a}=\dfrac{1\frac{1}{5}}{\frac{3}{10}}=4 \\
m_b=\dfrac{y_b}{x_b}=\dfrac{6}{2\frac{2}{5}}=2\frac{1}{2} \\
\bullet \text{Länge der Vektoren:} \\
\left|\vec{a}\right| =\sqrt{x_a^2+y_a^2}=\sqrt{\left(\frac{3}{10}\right)^2+\left(1\frac{1}{5}\right)^2} =1,24 \\
\left|\vec{b}\right| =\sqrt{x_b^2+y_b^2} =\sqrt{\left(2\frac{2}{5}\right)^2+6^2} =6,46 \\
\bullet \text{Skalarprodukt:} \\
\vec{a} \circ \vec{b}==\left( \begin{array}{c} \frac{3}{10} \\ 1\frac{1}{5} \\ \end{array} \right) \circ \left( \begin{array}{c} 2\frac{2}{5} \\ 6 \\ \end{array} \right) =\frac{3}{10} \cdot 2\frac{2}{5} + 1\frac{1}{5} \cdot 6 = 7\frac{23}{25} \\
\bullet \text{Fläche des Parallelogramms aus } \vec{a},\vec{b} \\
A= \left| \begin{array}{cc} \frac{3}{10} & 2\frac{2}{5} \\ 1\frac{1}{5} & 6 \end{array} \right| = \frac{3}{10} \cdot 6 - 1\frac{1}{5} \cdot 2\frac{2}{5} = -1\frac{2}{25} \\
\text{ Fläche des Dreiecks aus } \vec{a},\vec{b}\\
A=\frac{1}{2} \left| \begin{array}{cc} \frac{3}{10} & 2\frac{2}{5} \\ 1\frac{1}{5} & 6 \end{array}\right| =\frac{1}{2}(\frac{3}{10} \cdot 6 - 1\frac{1}{5} \cdot 2\frac{2}{5}) = -\frac{27}{50} \\
\bullet \text{Schnittwinkel:} \\
\cos \alpha= \displaystyle\frac{ \vec{a} \circ \vec{b}}{ \left|\vec{a}\right| \cdot \left|\vec{b}\right|}\\
\cos \alpha= \dfrac{\frac{3}{10} \cdot 2\frac{2}{5} + 1\frac{1}{5} \cdot 6 }{\sqrt{\left(\frac{3}{10}\right)^2+\left(1\frac{1}{5}\right)^2}\cdot\sqrt{\left(2\frac{2}{5}\right)^2+6^2}} \\
\cos \alpha= \left|\displaystyle\frac{7\frac{23}{25}}{1,24 \cdot 6,46} \right| \\
\cos \alpha= \left| 0,991 \right| \\
\alpha=7,77 \\
\end{array}$