title: SymPy returns no solution for a simple set of trigonometric equations
body: <p>I'm trying to solve the following equations:</p>
  <p>cos(a) - cos(b) - 1 = 0</p>
  <p>and</p>
  <p>sin(a) - sin(b) = 0</p>
  <p>Using SymPy I get no solutions for <code>(a,b)</code>.</p>
  <pre><code>from sympy import symbols, sin, cos, solve, Eq
  
  a, b = symbols(&quot;a b&quot;)
  eq1 = Eq(cos(a) - cos(b) - 1, 0)
  eq2 = Eq(sin(a) - sin(b), 0)
  solve([eq1, eq2], [a, b])
  </code></pre>
  <p>However, there exists at least one solution:</p>
  <p>a = 60°</p>
  <p>b = 120°</p>
  <p>Why can't SymPy solve the set of trigonometric equations?</p>