Can a directed line have direction angles 45°, 45°, 60°? fro

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 Multiple Choice QuestionsShort Answer Type

1. If a line makes angles 90°, 135°, 45° with x, y and z-axes respectively, find its direction cosines.
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2.

Can a directed line have direction angles 45°, 60°, 120°?

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3. Can a directed line have direction angles 45°, 45°, 60°?


Let l, m, n be the direction cosines of the line with direction angles 45°, 45°, 60°.
     therefore space space straight l space equals cos space 45 degree space equals fraction numerator 1 over denominator square root of 2 end fraction comma space straight m space equals space cos space 45 degree space equals space fraction numerator 1 over denominator square root of 2 end fraction comma space straight n space equals space cos space 60 degree space equals space 1 half
These values of l, m, n do not satisfy the selection l2 + m2 + n2 = 1 as
    open parentheses fraction numerator 1 over denominator square root of 2 end fraction close parentheses squared plus space open parentheses fraction numerator 1 over denominator square root of 2 end fraction close parentheses squared plus space open parentheses 1 half close parentheses squared space equals space 1 half plus 1 half plus 1 fourth space equals 5 over 4 not equal to 1
∴ given angles cannot be the direction angles of a line.
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4.

A line makes an angle of straight pi over 4 with each of y-axis and z-axis. Find the angle made by it with x-axis. 

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5. Find the direction cosines of x, y and z-axis.
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6. Find the direction-cosines of a line which makes equal angles with the axes. How many such lines are there?
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7.

If a line has direction ratios 2, -1, -2, determine its direction cosines. 

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8.

If a line has direction ratios 2, -1, -2, determine its direction cosines. 

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9. If a line has the direction ratios – 18, 12, – 4. then what are its direction cosines?
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10. Find the direction ratios and the direction cosines of the lines joining the pairs of points:
 (–2, 1, 0), (3, 2, 1).
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