ans plz..................3d geometry
Answers
Answer:
Direction cosines are denoted as l,m,n where l, m, n refer to the cosine value of angles measured by the line on the x-axis, y-axis, z-axis respectively.
One important result to be remembers based on l, m, n is:
→ l² + m² + n² = 1
Coming to the question,
Angle made by the line with the positive x-axis is 2π/3
→ Cos ( 2π/3 ) = Cos ( π - π/3 ) = -1/2
Hence l = (-1/2)
Angle made by the line with the positive y-axis is π/3
→ Cos ( π/3 ) = 1/2
Hence m = 1/2
Now we are not given the angle made by line with the positive z-axis. Hence we use the result we know.
→ l² + m² + n² = 1
→ ( -1/2 )² + ( 1/2 )² + n² = 1
→ ( 1/4 ) + ( 1/4 ) + n² = 1
→ ( 1/2) + n² = 1
→ n² = 1 - ( 1/2 )
→ n² = 1/2
⇒ n = ± √( 1/2 )
⇒ n = ± ( 1/√2 )
Hence Option (A) is the right answer.
OPTION A IS THE ANSWER
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