Chapter 2.4.3 Kcalc
===================

Kcalc is a scientific calculator application.

Features:

 - trignometric functions
 - factorials
 - built in mathematical and scientific constants.
 - memory
 - copy and paste

Useage
------
To do simple arithmetic click the numbers and then press the sign for addition, multiplication, subtraction,  or division. You can also type in the numbers and press :guilabel:`+` for addition, :guilabel:`-` for subtraction, :guilabel:`x` for multiplication and :guilabel:`/` for division. To view the answer press the button that is an :guilabel:`=`. 
 
.. image:: Kcalc.png

To make a number negative press the button that looks like a :guilabel:`+/-`. To insert decimals press the decimal point button which looks like . when you get to the part which is less than a whole number. To clear input from Kcalc Press the button with a C on it. To group operations so they happen together use the parenthesis to make things grouped to gether for example 2*(2+3) would give the result of 10 because it would add 2 and 3 and then multiply by two.

To copy and answer out of Kcalc press :kbd:`control + c` or :menuselection:`edit --> copy` from the menu. To paste a number into Kcalc you can press :kbd:`control + v` or :menuselection:`edit --> paste` from the menu. To cut the text from Kcalc press :kbd:`control +x` or :menuselection:`edit --> cut` from the menu.

Scientific calculator mode advanced fuctionality
------------------------------------------------

If you want even more functionality of Kcalc there is also scientific mode which is acessed from :menuselection:`settings --> scientific mode` radio button. The button :guilabel:`1/x` takes takes 1 and divides it by the number currently on the calculator also known as taking the reciprocal. :guilabel:`x!` read x factorial will take the number X you entered and multiple each number going down to 1 for example 5! would multiply 5*4*3*2*1. 

The x squared button will take a x*x and multiply it by itself. The button with x and a superscript y will take x the number you have in will exponeniate x to the power of y. The x 10 with a supercript y will end up multiplying x by 10 to the power of y so for example to multiply 5 by 10 to the power of 3 entering in will give the answer of 5,000.

To change the unit that angles are measured in for triginometric units in Kcalc. Degrees take 360 to form a full circle while, 2Π radians form a full circle and 400 gradians form a full circle. The radio button for Deg is to select Degrees as the unit for angles, Rad selects :guilabel:`radian` as the unit of measurment of angles and :guilabel:`Grad` selects Gradians as the unit of measurement for angles. The :guilabel:`Sin` button takes what you have as the input and takes the trigonometric sine function of that value measured in the unit for angles you have selected. The :guilabel:`cos` button takes the cosine of the vlaue in the unit of angle you have selected. The :guilabel:`tan` button takes the tangent of the angle in the current units.  

.. image:: kcalc-scientific.png

Version
-------
Lubuntu ships with version 18.04.3 of Kcalc.

How to launch
-------------
To launch kcalc go to :menuselection:`accessories --> Kcalc` or run

.. code::

   kcalc 
 
from the command line. The icon for kcalc looks like a box with a + sign a - sign a multipliucation sign and an equals sign.
