**BUG**
Concise problem statement:
Click and drag of WaveForm cursor from lower left to upper right shows dy is negative.
This is wrong: dragging WaveForm cursor from lower left to upper right should show dy as positive.
Steps to reproduce bug:
1. Run transient sim;
2. Click and drag WaveForm cursor lower left to upper right.
Results:
Observe that dy is negative.
Expected results:
For lower left to upper right drag, dy should be positive.
Url:
https://easyeda.com/file_view_Use-SIN-source-to-generate-COS_mkewqHZhz.htm
Browser:
Brand new interactions and interfaces. 
Easy to use and quick to get started. 
