Need help with arctan, arccos, arcsin

[ladventchildp]

ok
well my first questions dealing with inclination, i get how to do it though im having trouble calculating arctan.
so the question goes as follow

Find the inclination of the line 2x+3y=6.

***Solution****
tan(@)=-2/3
@=pie+arctan(-2/3)

though i cant calculate arctan of -2/3 so can someone explain me how to calculate arctan. thank you and if you can give me an inside for arc sin and cos that would be great thanks.

 

[morson]

I obviously wouldn't have a clue without a calculator. I had a look at a table of angle values and I'd say the angle "arctan(-2/3)" is close to -34 degrees?

 

[pka]

can someone explain me how to calculate arctan.

This is the standard series representation for the arctangent function:
\(\displaystyle \L \arctan (x) = \sum\limits_{k = 0}^\infty {\frac{{\left( { - 1} \right)^k x^{2k + 1} }}{{\left( {2k + 1} \right)}}}.\)
This is the routine that calculators use to determine the values of the arctangent.
Because it is an alternating series, using finitely many terms gives a good approximation.