What is the cosine of angle between the planes x+ y + z + 1 = 0 and 2x -2y + 2z + 1= 0 ?

### Question Asked by a Student from EXXAMM.com Team

Q 2349445313.     What is the cosine of angle between the planes
x+ y + z + 1 = 0 and 2x -2y + 2z + 1= 0 ?
NDA 2012 Paper 1
A

1/2

B

1/3

C

2/3

D

None of these

#### HINT

(Provided By a Student and Checked/Corrected by EXXAMM.com Team)

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