title: Why Am I Getting a NoMethodError?
body: <pre><code>class UnitCircle
      def prompt
          puts "Enter a number: "
          @number = gets
          @number = @number.to_i
          puts "Enter a trigonometric equation to perform on that number: "
          @eqn = gets
      end
  end
  uc = UnitCircle.new
  uc.prompt
  num = Math.send(uc.instance_eval {@eqn}, uc.instance_eval {@number})
  </code></pre>
  
  <p>When I try to run it with say,</p>
  
  <pre><code>@number = 30
  @eqn = sin
  </code></pre>
  
  <p>I get a no method error, why?</p>