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Question
A=(x1,y1z1) and B=(x2,y2,z2) are two points. lf l,m,n are the d.cs of CD and l(x2−x1)+m(γ2−y1)+n(z2−z1)=0, then the cosine of the angle between the lines AB and CD is:
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Solution
The correct option is C 90o
Direction cosines of the line CD are (l,m,n) and thus direction ratios of the line CD are (l,m,n)
Now d.r. s of the line AB are ((x2−x1),(y2−y1),(z2−z1))
Since, l(x2−x1)+m(y2−y1)+n(z2−z1)=0
Thererfore, cosθ=0
⇒θ=π2
Ans: A
Direction cosines of the line CD are (l,m,n) and thus direction ratios of the line CD are (l,m,n)
Now d.r. s of the line AB are ((x2−x1),(y2−y1),(z2−z1))
Since, l(x2−x1)+m(y2−y1)+n(z2−z1)=0
Thererfore, cosθ=0
⇒θ=π2
Ans: A
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