Question

$A=(x_1,y_1,z_1)$ and $B=(x_2,y_2,z_2)$ are two points. If l,m,n are the d.cs of CD and $l(x_2-x_1)+m(y_2-y_1)+n(z_2-z_1)=0$ then the cosine of the angle between the lines AB and CD is

• A. $90^{\circ }$
• B. 1
• C. 0
• D. 1/2

Answer 1

Answer: (C)

$\theta =90^{\circ }\Rightarrow \cos \theta =0$