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11.3-bo'lim : Nuqta mahsuloti

4. \(\vec v = \left\langle {1,2,3,4} \right\rangle \) va \(\vec w = \left\langle {0, - 1,4, - 2} \right\rangle \) orasidagi burchakni aniqlang.

Yechim

Bu erda juda ko'p narsa qilish kerak emas. Biz qilishimiz kerak bo'lgan narsa bu formulani nuqta mahsulotining geometrik talqinidan quyidagicha qayta yozish:

\[\cos \theta = \frac{{\vec v\centerdot \vec w}}{{\left\| {\vec v} \right\|\,\,\left\| {\vec w} \right\|}}\]

Bu bizga ikki vektor orasidagi burchakni tezda aniqlash imkonini beradi.

Bizga birinchi navbatda quyidagi miqdorlar kerak bo'ladi (bu hisob-kitoblarda qatnashgan arifmetikani tekshirishni sizga qoldiramiz...).

\[\vec v\centerdot \vec w = 2\hspace{0.25in}\hspace{0.25in}\left\| {\vec v} \right\| = \sqrt {30} \hspace{0.25in}\hspace{0.25in}\left\| {\vec w} \right\| = \sqrt {21} \]

Vektorlar orasidagi burchak u holda,

\[\cos \theta = \frac{2}{{\sqrt {30} \,\sqrt {21} }} = 0.07968\hspace{0.25in} \Rightarrow \hspace{0.25in}\theta = {\cos ^{ - 1}}\left( {0.07968} \right) = \require{bbox} \bbox[2pt,border:1px solid black]{{1.49103\,\,{\rm{radians}}}}\]