,
sin (90 – θ) = cos θ
i e sin φ =
|
| |
|
bb n
n
⋅
rr r
r
 or φ = 
sin–1
b n
b n
⋅
Example 25 Find the angle between the line
1
2
x +
 =
3
3
6
y
z −
=
and the plane 10 x + 2y – 11 z = 3 Solution Let θ be the angle between the line and the normal to the plane