I was using the TI-84 Plus calculator to check for Y-Axis symmetry in the graph of "cos(2X+1)" and as I had to do it fast (I was in the middle of a test), I quickly noted that it was symmetrical. I had set the zoom to "ZTrig". This is (exactly)what I saw :
But it turned out that the graph was not symmetrical. This is the graph by Google Graphs.
How do I identify correctly if a graph is symmetrical about an axis(Mostly the Y-axis) or not in the TI-84 Plus
Update 1 :
@Summea, This is what I got when I used the table method. This works fine, but is there a way to get the accuracy more than 5 digits as some problems may require it?
@Amzoti, I set the window variables like this (I changed the "Xscl" to 180, from 90, to see if it zooms in, but for some reason, the graph remains the same.
The small bars on the graph which indicate the points have really moved, but the graph remains the same.
I also tried another method, i.e. using the "ZBox" function to select a box and zoom in there. This is what I saw:
The graph hardly shows any difference, even now. How can I solve this?