In the following cases, determine whether the given planes are parallel or perpendicular, and in case they are neither, find the angles between them.

7x + 5y + 6z + 30 = 0 and 3x – y – 10z + 4 = 0

The eq. of the given planes are

7x + 5y + 6z + 30 = 0 and 3x – y – 10z + 4 = 0

Two planes are ⊥ if the direction ratio of the normal to the plane is

a_{1}a_{2} + b_{1}b_{2} + c_{1}c_{2} = 0

21 – 5 – 60

-44 ≠ 0

∴ Both the planes are not ⊥ to each other.

Two planes are || to each other if the direction ratio of the normal to the plane is

∴ Both the planes are not || to each other.

The angle between them is given by

13