If vectors overrightarrow {A} = cosomega | vedclass

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Question

$\begin{gathered}
  \,\,\,\,\,Two\,vectors\,\bar A\,and\,\bar B\,are\,orthogonal \hfill \
  to\,each\,other,\,if\,their\,scalar\,product

Vedclass · Accepted Answer

$t=$$\;\frac{\pi }{\omega }$

Vedclass · Answer

$\begin{gathered}
  \,\,\,\,\,Two\,vectors\,\bar A\,and\,\bar B\,are\,orthogonal \hfill \
  to\,each\,other,\,if\,their\,scalar\,product \hfill \
  is\,zero\,i.e,.\,\bar A\,.\,\bar B = 0. \hfill \
  Here,\,\bar A = \cos \omega t\,\hat i + \sin \omega t\,\hat j \hfill \
  \,\,\,\,\,\,\,\,\,and\,\bar B = \cos \frac{{\omega t}}{2}\hat i + \sin \frac{{\omega t}}{2}\hat j \hfill \
  	herefore \,\bar A\,.\,\bar B = \left( {\cos \omega t\hat i + \sin \,\omega t\,\hat j} ight) \cdot \left( {\cos \frac{{\omega t}}{2}\hat i + \sin \frac{{\omega t}}{2}\hat j} ight) \hfill \
  \,\,\,\,\,\,\,\,\,\,\,\,\,\, = \,\cos \,\omega t\,\cos \,\frac{{\omega t}}{2} + \sin \,\omega t\,\sin \,\frac{{\omega t}}{2} \hfill \
  \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\left( {\because \,\hat i \cdot \hat i = \hat j \cdot \hat j = 1\,and\,\hat i \cdot \hat j = \hat j \cdot \hat i = 0} ight) \hfill \ 
\end{gathered} $

$\begin{gathered}
  \,\,\,\,\,\,\,\,\,\,\,\,\,\, = \cos \left( {\omega t - \frac{{\omega t}}{2}} ight) \hfill \
  \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\left( {\because \cos \left( {A - B} ight) = \cos A\cos B + \sin A\sin B} ight) \hfill \
  But\,\bar A\,.\,\bar B = 0\left( {as\bar A\,\,and\,\bar B\,are\,orthogonal\,to\,each\,other} ight) \hfill \
  	herefore \,\,\,\cos \left( {\omega t - \frac{{\omega t}}{2}} ight) = 0 \hfill \
  \,\,\,\,\,\,\cos \left( {\omega t - \frac{{\omega t}}{2}} ight) = \cos \frac{\pi }{2}\,or\,\omega t - \frac{{\omega t}}{2} = \frac{\pi }{2} \hfill \
  \,\,\,\,\,\,\frac{{\omega t}}{2} = \frac{\pi }{2}or\,t = \frac{\pi }{\omega } \hfill \ 
\end{gathered} $

If vectors $\overrightarrow {A} = cos\omega t\hat i + sin\omega t\hat j$ and $\overrightarrow {B} = cos\frac{{\omega t}}{2}\hat i + sin\frac{{\omega t}}{2}\hat j$ are functions of time, then the value of $t$ at which they are orthogonal to each other is

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