# Show that no line in space can make angles π6 and π4 with X-axis and Y-axis. - Mathematics and Statistics

Sum

Show that no line in space can make angles pi/6 and pi/4 with X-axis and Y-axis.

#### Solution

Let, if possible, a line in space make angles pi/6 and pi/4 with X-axis and Y-axis.

∴ α = pi/6, beta = pi/4

Let the line make angle γ with Z-axis

∵ cos2α + cos2β + cos2γ = 1

∴ "cos"^2(pi/6) + "cos"^2(pi/4) + "cos"^2gamma = 1

∴ (sqrt3/2)^2 + (1/sqrt2)^2 + "cos"^2gamma = 1

∴ "cos"^2gamma = 1 - 3/4 - 1/2 = - 1/4

This is not possible, because cos γ is real.

∴ cos2γ cannot be negative.

Hence, there is no line in space which makes angles pi/6 and pi/4 with X-axis and Y-axis.

Concept: Vectors and Their Types
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