Question:
If a line x p + 1 = y q – 1 = z r – 2 Where p = 2q = 3r makes an angle with the position direction of the y-axis then what is cos 2q equal to?
If a line x p + 1 = y q – 1 = z r – 2 Where p = 2q = 3r makes an angle with the position direction of the y-axis then what is cos 2q equal to?
Options:
- a) -31 49
- b) -37 49
- c) 31 49
- d) 37 49
- a) -31 49
- b) -37 49
- c) 31 49
- d) 37 49
correct answer : a)
Explanation:
D.rs of line are p, q, r
where p = 2q = 3r Þ
pq r
63 2= =
\ D.rs of line are 6, 3, 2
\ cos q = 3
63222 2++
=
3
7
cos2q = 2 cos2q – 1 = 18
49 1-
=
-31
49
D.rs of line are p, q, r
where p = 2q = 3r Þ
pq r
63 2= =
\ D.rs of line are 6, 3, 2
\ cos q = 3
63222 2++
=
3
7
cos2q = 2 cos2q – 1 = 18
49 1-
=
-31
49