The sum of the direction cosines of a st

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Target Exam

CUET

Subject

-- Mathematics - Section B1

Chapter

Three-dimensional Geometry

Question:

The sum of the direction cosines of a straight line is

Options:

zero

one

constant

none of these

Correct Answer:

constant

Explanation:

cos α = l, cos β = m, cos γ = n

sum of direction cosines cos α + cos β + cos γ

= l + m + n

which is constant.