\(\rm \vec{a} \ and \ \vec{b} \ is \ \dfrac{2\pi}{3}\)  మధ్య కోణం \(\vec{a}\) ప్రొజెక్షన్ \(\vec{b}\)   -2, ఉంటే అప్పుడు \(|\vec{a}|=\)

  1. 4
  2. 3
  3. 2
  4. 1

Answer (Detailed Solution Below)

Option 1 : 4
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Detailed Solution

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పద్ధతి:

 \(\rm \vec{a}\) ప్రొజెక్షన్​ అయిన \(\rm \vec{b}\)  దిశ = \(\rm\dfrac {1}{|\vec b|}(\vec a.\vec b)\)

సాధన:

ఇచ్చిన కోణం \(\rm \vec{a} \ and \ \vec{b} \ is \ \dfrac{2\pi}{3}\) మరియు ప్రొజెక్షన్​ \(\vec{a}\) \(\vec{b}\)యొక్క దిశ -2

సమాచారం ప్రకారం, 

 \(\vec{a}\) ప్రొజెక్షన్​ అయిన \(\rm \vec{b}\)\(\rm\dfrac {1}{|\vec b|}(\vec a.\vec b)\) యొక్క దిశ

⇒ - 2 = \(\rm\dfrac {1}{|\vec b|}(|\vec a||\vec b|\;cos\;\dfrac {2\pi}{3})\)

⇒ - 2 = \(\rm |\vec a|\;cos\;\dfrac {2\pi}{3}\)

⇒ - 2 = \(\rm |\vec a|\;(\dfrac {-1}{2})\)

⇒  \(\rm |\vec a| = 4\)

కావునn \(\rm \vec{a} \ and \ \vec{b} \ is \ \dfrac{2\pi}{3}\) మధ్యకోణం \(\vec{a}\) ప్రొజెక్షన్​ అయిన \(\vec{b}\) దిశ -2, అయిన \(|\vec{a}|=\) 4

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