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Three Dimensional Geometry

Question
CBSEENMA12033409

In the following cases, determine whether the given planes are parallel or perpendicular, and in case they are neither, find the angles between them:
2x + y + 3z – 2 = 0 and x – 2y + 5 = 0

Solution

The equations of given planes are
2x + y + 3z – 2 = 0    ...(1)
and x – 2y + 5 = 0    ...(2)
Direction ratios of normal to plane (1) are 2, 1, 3
Direction ratios of normal to plane (2) are 1, – 2, 0.
Now, 2 over 1 not equal to fraction numerator 1 over denominator negative 2 end fraction not equal to 3 over 0
∴    planes (1) and (2) are not parallel.
Again (2) (1) + (1) (– 2) + (3) (0) = 2 – 2 + 0 = 0
∴ given planes (1) and (2) are perpendicular to each other.