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.

[parisse]

equation( LineTan sin(t),t=pi/4 )

Note that LineTan uses TI convention, i.e. should be enter without parenthesis: there is no bug here, the title should be modified:-)

[quinyu]

I did not know about the "no parentheses" rule. When clicking on the toolbox, the parenthesised one is added to the entry line. My bad. And even the CAS reapplies the parentheses when I enter such line ( equation(LineTan sin(x),0) comes back as equation(LineTan(sin(x),0)) )... confusing, to say the least.

All the same, equation(LineTan Sin(x),pi) still returns an error, even though (as shown above) the function does have a tangent at the place with a proper form. equation(LineTan Cos(x),pi) works. Many other fractions/multiples of pi also work and deliver the proper tangent equation. I might be doing something wrong, or the CAS does.