The plane 2 x − 2 y + z = 3 is rotated about the line where it cuts the xy plane by an acute angle α . If the new position of plane contains the point ( 3 , 1 , 1 ) then 9 cos α equal to .......

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Let equation of new plane 2 x − 2 y + z − 3 + λ z = 0 Point ( 3 , 1 , 1 ) lie on it ⇒ λ = − 2 Hence equation of new plane 2 x − 2 y − z = 3 cos α = 3.3 4 + 4 − 1 ​ = 9 7 ​

Mathematics - 3D-Coordinate Geometry Question with Solution | TestHub

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