Find the direction cosines of the vector 4{i} - 3{j}.

Correct Answer is : 45,− 35\;4/5,-\;3/554,−53

Correct Answer is : 45,− 35\;4/5,-\;3/554,−53

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WAEC Further Mathematics 2010 Paper

Question : 27

Total: 40

4\hat{i} - 3\hat{j}

Solution:

Given $V = x\hat{i} + y\hat{j}$ , the direction cosines are $\;\frac{x}{|V|},\;\frac{y}{|V|}$ .

$|4\hat{i} - 3\hat{j}| = \sqrt{4^{2} + (-3)^{2}} = \sqrt{25} = 5$

Direction cosines = $\;\frac{4}{5},\;\frac{-3}{5}$ .

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