Bug with LineTan

[quinyu]

Using software 2015-6-17 (8151), HW ver C, CAS 1.1.2-11, OS 0.037.526;

1. Pressing an Enter on a previously entered LineTan command (for example: LineTan(Sin(x),0) ) drops the outer parentheses, making it very inconvenient if you wish to check out the tangents at a number of places.

2. The previous expression, but with pi, or x,pi creates "Error: Bad Argument Value". Which is weird since the sine function clearly has a tangent at x=pi. If I want to get the equation, then f'(pi)*(x-pi)+f(pi)=(-1)*(x-pi)+0. Thus the tangent has the equation L(x)=pi-x at x=pi.

Furthermore I would find it valuable if LineTan would perhaps have an option to output the equation (so no need to click on images to get the equation that way), or another function would do so. I understand that the LineTan function is primarily meant to be used in the graphing context, not within the CAS.