# How do you find the angle between the planes #x + 2y - z + 1 = 0# and #x - y + 3z + 4 = 0#?

##### 1 Answer

See below

#### Explanation:

Angle between two planes is given by the angle of their normal vectors (caracteristic). The caracteristic vectors are given by coefficients of x, y and z in equation plane

In our case

and

By other hand we know that dot product vector is given by

The dot product also can write as

From (1)