The Andes solve tool will only solve for a variable when it has enough information to determine a unique solution. This requires the following techniques:

To solve for an angle:

    Andes does not provide inverse trignometric functions (arctan, arccos, arcsin) since these are not single-valued functions -- trignometric functions generally don't have unique inverses in the range of angles from 0 to 360 degrees. For example:

    tan(qv) = 0.75355 ....
    Can't solve for qv, since can't determine whether qv = 37 deg or 217 deg

To solve for an angle in Andes, you usually need to enter calculable expressions for both the sin and the cosine of the angle. Example:

    sin(qv) = 3/5
    cos(qv) = 4/5
    Now Andes can solve for qv.

    You don't need to give explicit numerical values for the sin and cos of the angle as long as you have an expression containing the sin and another containing the cos, plus enough other equations to determine the values for other unknowns. Usually if you write equations determining the value of the vector components, plus standard projection equations relating the components to the magnitudes, that should be sufficient. Example:

   v_x = 3 m/s
   v_y = 4 m/s
   v_x = v*cos(qv) 
   v_y = v*sin(qv)
    Now Andes has enough to solve for qv (and also for v, for that matter).

To solve when a quadratic equation is involved:

Make sure you enter relations between vector components and vector magnitudes. The Andes solver knows that vector magnitudes must be positive, so this information can enable it do determine which of two possible roots to use in  a solution. Example:

    v_x^2 = 4
   Can't solve for v_x, since can't determine whether v_x = +2 or v_x = -2

    v_x^2 = 4
    v_x = v
    Now can solve for v_x, since Andes knows v is positive, so v_x must be +2.

If you can't solve and don't know why:

• Make sure you have entered equations for all given values you need.
• Make sure you have related all vector component variables to vector magnitude variables if you have used both.
• Look for any variables remaining in the solve-for result. These mean the solver could not eliminate these variables, so check to make sure you have entered equations to determine their values.