The angle of the resultant vector is equal to the inverse tangent of the quotient of the x-component divided by the y-component of the resultant vector
the inverse cosine of the quotient of the y-component divided by the x-component of the resultant vector.
the inverse cosine of the quotient of the x-component divided by the y-component of the resultant vector.
the inverse tangent of the quotient of the y-component divided by the x-component of the resultant vector.

The angle of the resultant vector is equal to the inverse tangent of the quotient of the y-component divided by the x-component of the resultant vector.

To find the angle of a resultant vector, the vector must be resolved into y-component and x-component.

The angle of this resultant vector is also known as the direction of the vector.

Mathematically, the direction of a resultant vector is given as;

Therefore, the angle of the resultant vector is equal to the inverse tangent of the quotient of the y-component divided by the x-component of the resultant vector.

Lear more here:

heat the gas and measure the pressure