Find the angle between the planes `x+y+2z=9a d n2x-y+z=15.`

Options

A. `(pi)/6`
B. `(pi)/3`
C. `(pi)/4`
D. none of these

Answer

B

Explanation

Let `theta` be the angle between the planes `x+y+2z=9` and `2x-y+z=15`. Then
`cos theta=((1)(2)+(1)(-1)+(2)(1))/(sqrt(1^(2)+1^(2)+2^(2))sqrt(2^(2)+(-1)^(2)+1^(2)))=1/2impliestheta=(pi)/3`