src/Vector.php
public function angleBetween(self $b)
    {
        $denominator = $this->length() * $b->length();
        if ($denominator == 0) {
            throw new Exception('Cannot divide by zero');
        }

        return acos($this->dotProduct($b) / $denominator);
    }
public function angleBetween(self $b)
    {
        $denominator = $this->length() * $b->length();
        if ($denominator == 0) {
            throw new Exception('Cannot divide by zero');
        }

        return acos($this->dotProduct($b) / $denominator);
    }
Returns the angle between the two vectors.

@api
@param self $b The vector to compute the angle between.
@return float The angle between the two vectors in radians.
@throws Exception if either of the vectors are zero-length.
@throws Exception if the vectors are not in the same vector space.
@see self::_checkVectorSpace() For exception information.