Signed doesn't work correctly

SystemVerilog
,
1

I have the following function:

   function tx_upconv_out_transaction predict(tx_upconv_in_transaction in_trx);
      tx_upconv_out_transaction predicted = tx_upconv_out_transaction::type_id::create("predicted");
      //-------golden model-----
//      predicted.y = (in_trx.xi * in_trx.cos - in_trx.xq * in_trx.sin)/ (2 ** 17);
      $display(" xi = %d, cos = %d xq = %d sin = %d", $signed(in_trx.xi),$signed(in_trx.cos),$signed(in_trx.xq),$signed(in_trx.sin) );
      predicted.y = ($signed(in_trx.xi) * $signed(in_trx.cos) - $signed(in_trx.xq) * $signed(in_trx.sin))/ (131072);      
      return predicted;
   endfunction: predict

Where: The field in in_trx are defined by:

bit [15:0] xi;
bit [15:0] xq;
bit [15:0] sin;
bit [15:0] cos;
For the input:

xi, xq = fffa (hex)
sin = 0
cos = 7ffe (hex)
The output (display) is:

xi = -6, cos = 32766 xq = -6 sin = 0
Where it should be:

xi = -6, cos = -2 xq = -6 sin = 0

2

In reply to saritr:

The value of cos (16’h7ffe) is 32766. The hex value for -2 is 16’hfffe.