I know how to find magnitude of resultant of two forces . But I was doubt what is the direction of resultant force?

One technique is this:

1. Break each force into its x-component and y-component.

2. Sum up the x-component forces to get an Fx_total.

3. Sum up the y-component forces to get an Fy_total.

4. The resultant force is found using Pythagorus:

F_total = sqrt(Fx_total^2 + Fy_total ^2)

The direction is found using the arc tangent:

Theta = ArcTan(Fy_total/Fx_total)

You will need to check the value of theta to make sure that it's in the appropriate quadrant (plus or minus 180 degrees).