title: Mathematica Solve function gives incorrect solution, why?
body: <p>Please look into attached file. I’m using Mathematica Solve function to solve some simple equations from physics. One of the equations is an If function which defines function value when a condition is met. Solve finds almost correct solution which itself is a ConditionalExpression. For independent variable θ = 90° the answer given by Solve is in error. It seems that Solve forgets the case when Cos equals 0. Why? Thanks.</p>
  
  <p>Regards/Mikael
  <a href="https://i.stack.imgur.com/knX3Q.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/knX3Q.jpg" alt="Friction Model"></a></p>