Math, asked by Ayushvidulkar, 2 months ago

Find d.c.s of a line whose direction angles with X-axis Y-axis are 45° and 60°​

Answers

Answered by MaheswariS
0

\textbf{Given:}

\mathsf{Direction\;angles\;of\;a\;line\;are\;45^\circ\;and\;60^\circ}

\textbf{To find:}

\textsf{Direction cosines of the line}

\textbf{Solution:}

\mathsf{Let\;the\;direction\;angles\;of\;the\;line\;be\;\alpha,\beta\;and\,\gamma}

\mathsf{Here,\;\alpha=45^\circ,\,\beta=60^\circ}

\mathsf{Then,}

\mathsf{cos\alpha=cos45^\circ=\dfrac{1}{\sqrt{2}}}

\mathsf{cos\beta=cos60^\circ=\dfrac{1}{2}}

\mathsf{We\;know\;that,}

\boxed{\textbf{Sum of the squares of direction cosines is 1}}

\implies\mathsf{cos^2\alpha+cos^2\beta+cos^2\gamma=1}

\mathsf{\left(\dfrac{1}{\sqrt2}\right)^2+\left(\dfrac{1}{2}\right)^2+cos^2\gamma=1}

\mathsf{\dfrac{1}{2}+\dfrac{1}{4}+cos^2\gamma=1}

\mathsf{\dfrac{3}{4}+cos^2\gamma=1}

\mathsf{cos^2\gamma=1-\dfrac{3}{4}}

\mathsf{cos^2\gamma=\dfrac{1}{4}}

\mathsf{cos\gamma=\pm\dfrac{1}{2}}

\therefore\mathsf{Direction\;cosines\;of\;the\;line\;are}

\mathsf{\left(\dfrac{1}{\sqrt2},\dfrac{1}{2},\dfrac{1}{2}\right)\;(or)\;\left(\dfrac{1}{\sqrt2},\dfrac{1}{2},\dfrac{-1}{2}\right)}

\textbf{Find more:}

Find the direction cosines of the vector i^ +2j^+3k^

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