F1 has a magnitude of 9N acting due west, and F2 has a magnitude of 12 N.

I know the magnitude is 15 but I don't know the angle and how to calculate it. I need a lot of help for calculating resultant angles.

well, its angle θ is

tanθ = 12/-9

did you actually try drawing a diagram?

I assume you can convert from the conventional trig angles to compass directions ...

To calculate the angle of the resultant force, you can use trigonometric functions like sine, cosine, or tangent. In this case, we can use the tangent function.

First, let's draw a diagram to understand the situation better. Place F1 and F2 head to tail, with F1 pointing due west and F2 having an unknown direction. We can label the angle between the resultant force and the horizontal axis as θ.

To find θ, we can use the tangent function:

tan(θ) = opposite/adjacent.

In this case, the opposite side is F1 (9 N) and the adjacent side is F2 (12 N). Therefore, we have:

tan(θ) = 9/12.

Now, we need to find θ. To do this, take the inverse tangent (arctan) of both sides to isolate θ:

θ = arctan(9/12).

Using a calculator, find the arctan of 9/12 to get the value of θ in radians. If you want the angle in degrees, multiply the value in radians by 180/π (approximately 57.3 degrees).

So, to calculate the angle, use the equation θ = arctan(9/12) and either convert the result to degrees or leave it in radians, depending on your preference.