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Three Dimensional Geometry
Question
Find the direction-cosines of a line which makes equal angles with the axes. How many such lines are there?
Solution
Let α be the angle which the line with all the axes,
∴ its direction-cosines are cos α, cos α, cos α
required direction-cosines are 
These are four different groups of signs
i.e., +, +, +
+, -, +
+, +, -
+, -, -
∴ there are four distinct lines.
∴ its direction-cosines are cos α, cos α, cos α
required direction-cosines are These are four different groups of signs
i.e., +, +, +
+, -, +
+, +, -
+, -, -
∴ there are four distinct lines.
Some More Questions From Three Dimensional Geometry Chapter
Find the direction cosines of x, y and z-axis.
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Mock Test Series
Mock Test Series