Kinematics Question 129
Question: If $ \overrightarrow{A}=2\hat{i}+4\hat{j}-5\hat{k} $ the direction of cosines of the vector $ \overrightarrow{A} $ are
Options:
A) $ \frac{2}{\sqrt{45}},\frac{4}{\sqrt{45}}and\frac{-5}{\sqrt{45}} $
B) $ \frac{1}{\sqrt{45}},\frac{2}{\sqrt{45}}and\frac{3}{\sqrt{45}} $
C) $ \frac{4}{\sqrt{45}},0and\frac{4}{\sqrt{45}} $
D) $ \frac{3}{\sqrt{45}},\frac{2}{\sqrt{45}}and\frac{5}{\sqrt{45}} $
Correct Answer: A $ \vec{A}=2\hat{i}+4\hat{j}-5\hat{k} $ $ |\overrightarrow{A}|=\sqrt{{{(2)}^{2}}+{{(4)}^{2}}+{{(-5)}^{2}}}=\sqrt{45} $ $ \cos \alpha =\frac{2}{\sqrt{45}},\cos \beta =\frac{4}{\sqrt{45}},\cos \gamma =\frac{-5}{\sqrt{45}} $
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